The B58 Bolt-On Build: What to Add and in What Order

A Stage 1 flash on a B58 is worth up to 20 percent more horsepower on 93 octane by bootmod3's own numbers, about 400 crank horsepower on a 335 hp F22 M240i, for the price of software. Every part after that has a right moment and a wrong one. Bolt a catless downpipe onto a stock map and you get a check engine light; buy a heat exchanger for a car that never sees a second hard pull and you've bought a very nice radiator.

This guide sets the B58 bolt-on build order for the F chassis Gen 1 cars (M140i, M240i, 340i, 440i), the G chassis Gen 2 cars (M340i, M440i, G42 M240i, Z4 M40i) and the A90 Supra: what goes on first, what your engine generation changes, what it costs, and where bolt-ons stop. We sell the hardware, not tunes.

Gain figures come from bootmod3 dealer listings and MHD's store, prices and fitment from our own listings, and owner results from SupraMKV, F30Post and Bimmerpost. Prices vary by dealer. MHD bills in euros, so its prices are converted to US dollars and rounded.

Shop B58 Downpipes

The Short Answer

The B58 bolt-on build order is: check plugs and DME lock, flash Stage 1, add an aluminum charge pipe (needed on 2016 to 2019 Gen 1 cars, optional on Gen 2), then a catless downpipe, gasket and Stage 2 map, then a bigger heat exchanger. Intakes are for sound. Fuel comes last: a Gen 1 needs an HPFP past E30; Gen 2 cars run E50 on the stock pump.

The B58 Build Order at a Glance

Each B58 step below either makes the next one pay or protects the power you just added, which is why the order matters more than the brand.

The B58 Build, Step by Step

The B58 build runs from software to cooling to fuel, and the only steps that make real horsepower on their own are the map and the downpipe; everything else keeps that power working.

Step 0: Plugs, DME Lock and Flash Platform

Fit one step colder plugs with the first flash; Dinan's heat range 9 iridium plug is listed one step colder than OEM for Gen 1 and Gen 2 B58s, at $19.14 each. On 2020 and later cars, check the DME: MHD says units built after June 2020 need a Femto bench unlock, which US services quoted at about $800 to $1,600. bootmod3 is $595 at US dealers with one off the shelf map; MHD's flasher is about $315 and each map pack about $120. Our bootmod3 vs MHD guide compares them.

Step 1: Stage 1 Tune

Stage 1 is the biggest gain per dollar on the engine: bootmod3 claims up to 20 percent more horsepower on a Gen 1 B58 and 21 percent on the 2020 and later B58 on 93 octane. That is roughly 320 to 385 hp on an F30 340i and 382 to about 460 on a G20 M340i. bootmod3 doesn't say wheel or crank, so treat it as a ceiling.

Step 2: Charge Pipe (Gen 1 Yes, Gen 2 Maybe)

On a Gen 1 car, the factory plastic charge pipe is the part most likely to split once boost goes up, so it goes on with the Stage 1 flash. The do88 Gen 1 charge pipe ($478.25) fits the F20, F22, F30 and F32 cars plus Gen 1 G30 540i and G01 X3 M40i, and do88 measures 649 CFM against 528 stock. Our charge pipe guide explains why the plastic fails.

Gen 2 is different. SupraMKV owners have logged track seasons on the factory pipe at about 30 psi, and several report more leaks from aftermarket pipes than from stock. If you buy one anyway, Dinan's $269.95 system covers the G20, G22, G23 and G42, and Mishimoto ($349.95) and Injen ($458.72) cover the Supra.

Step 3: Catless Downpipe and Stage 2 Map

The downpipe is the one part that defines Stage 2. Our B58 4.5 inch catless downpipe is $199.99, adds 30 to 40 horsepower with a supporting tune per our listing, and fits Gen 1, Gen 2 and 48 volt mild hybrid B58s through the 2024 model year, but not the third generation B58 in 2025 and later cars. Order the single use 4.5 inch gasket (BMW 18328612538, $21.99) with it.

Flash the Stage 2 map the same day. bootmod3 claims up to 26 percent over stock on Gen 1 and 25 percent on Gen 2 on 93 octane, and its Gen 2 E50 map targets 24 psi. Our B58 Stage 1 vs Stage 2 guide covers the maps and our B58 downpipe guide covers sound, smell and install.

Step 4: Heat Exchanger, Then Auxiliary Radiators

Cooling comes right after Stage 2 because a tuned B58 loses power on repeat pulls before it loses anything else. The charge cooler lives inside the intake manifold on a small low temperature coolant loop, and a SupraMKV member who pulled the 2021 and later DME tables found timing cut by about 7.5 degrees at 5,500 rpm once intake air hits 134 F with coolant at 212 F.

The Dinan heat exchanger ($403.95) fits the Supra and G chassis cars, and Dinan says it cut charge air temperature by an average of 8.7 C over 30 back to back wide open pulls. Gen 1 cars use CSF's $695 triple pass unit. Track cars add a pair of auxiliary radiators next. Our B58 cooling guide covers the ladder; the S58 cooling guide explains the same water to air system.

Step 5: Intake

An intake on a B58 is a sound upgrade with a few horsepower attached, which is why it sits late in the order. Dinan claims up to 9 whp at 6,500 rpm for its $520.95 carbon intake on the G2x cars, without naming the map or fuel, and one Supra owner measured 3 hp on a stock car.

For Gen 1 cars, the aFe Momentum GT intake ($462) and do88's sealed Gen 1 intake ($426.98) both fit the M240i, 340i and 440i. Buy a sealed box with a heat shield; owners report open filters raising intake temperatures in traffic.

Step 6: Fuel

Fuel is the last bolt-on and the one that splits hardest by generation. On Gen 1 the cam driven high pressure fuel pump (HPFP) is the first limit, around E30, so bootmod3's regular Gen 1 Stage 2 maps stop there and E50 needs a Stage 2+ map with an upgraded HPFP, which runs $1,500 to $2,000 at list prices.

The in-tank pump comes next. F30Post owners put the stock Gen 1 tank pump's ceiling around 650 to 700 whp, and our B58 Stage 3 brushless LPFP guide covers the $574.99 kit, which fits F chassis Gen 1 cars only, not G chassis or Supra. Gen 2 cars run 350 bar injection and get an E50 Stage 2 map on the stock pump; full E85 there means an LPFP such as the DeatschWerks DW440 kit for 2020 to 2021 Supras plus port injection.

Fitment by Chassis: Gen 1, Gen 2, Supra and the 2025 Gen 3

The B58 build order is the same on every car, but the charge pipe, heat exchanger and fuel step change with the chassis and engine generation, and 2025 and later G20 and G22 cars are a separate engine.

Not sure which engine you have? Email us your VIN and we'll confirm fitment before you order.

What a B58 Bolt-On Build Costs

A Stage 2 street build on a Gen 1 B58 costs about $2,155 in parts and software at our prices, before labor: bootmod3 ($595), six plugs (about $115), the do88 charge pipe ($478.25), downpipe and gasket ($221.98), bootmod3's map bundle (about $50) and CSF's triple pass heat exchanger ($695). A G20 M340i skips the charge pipe and uses Dinan's $403.95 heat exchanger for about $1,385, plus $800 to $1,600 if the DME needs an unlock. Track cars add $490.95 to $778 for a pair of auxiliary radiators. Charge cooler manifolds ($2,325 for do88, $3,995 and up for CSF) are where "bolt-on" ends.

What Owners Actually Say

Owners mostly agree on the order and argue about two parts: the Gen 2 charge pipe and which cooling part comes first. These are paraphrased from SupraMKV, F30Post and G30 Bimmerpost threads.

The track day that wrote the shopping list. A 2022 Supra 3.0 owner took a completely stock car to a road course on an 80 F day, and after back to back 25 minute sessions the DME pulled fuel and timing and flashed an "Engine too hot" warning that took a long time to clear. The owner started a SupraMKV thread to find the fix. Replies split: one member called the intake manifold the only real fix and everything else a band aid, while a 2020 Z4 M40i owner on a Wagner manifold and a Stage 2 E50 map logged 122 to 126 F intake temps at Laguna Seca on a 75 F day. Our takeaway: heat shows up before power does, even on a stock car.

• 2020 Supra 3.0, aftermarket charge pipe on a stock turbo (SupraMKV). Bought a charge pipe the car didn't need and got an intermittent boost leak squeal. In the same thread, another owner had 41.7 track hours on the factory pipe at about 30 psi. Negative.
• 2023 Supra manual, aftermarket intake on a stock car (SupraMKV). Dyno proven 3 hp and a much better sound; intake temps stay near ambient moving but climb in stop and go traffic. Another owner called their intake's sound gain "minimal at best." Mixed.
• 2021 540i, MHD Stage 2, catted downpipe, charge pipe, flex fuel (G30 Bimmerpost). Calls it fun and fairly safe and knows owners near 100,000 miles on Stage 2. The cost: oil changes twice as often and a car that feels slow on 93 after E30 to E40. Mixed.
• 2017 M240i, Dorch HPFP, upgraded injectors and turbo, E40 (F30Post). The owner's tuner made 675 whp on the stock tank pump and wouldn't go further until the LPFP was upgraded. Fuel really is the last step.

Legal and Emissions

A catless downpipe is the step in this build that takes a B58 off the street, and a Stage 2 map that turns off the rear oxygen sensor monitor doesn't change that. This part is sold for off road and competition use only. Removing or defeating a catalytic converter on a vehicle driven on public roads violates the Clean Air Act, and many states inspect for it. Check your state and local laws before buying.

A catted pipe is sold as emissions legal for your state only with a CARB Executive Order or EPA verification, and we don't know of a B58 downpipe with a CARB EO. If your car gets inspected, stop at Stage 1 plus cooling and keep the factory downpipe.

Mistakes We See

• Buying the downpipe before the map. On a stock or Stage 1 map it throws P0420 and can overboost. The pipe and the Stage 2 map are one job.
• Skipping the charge pipe on a Gen 1. A split plastic pipe dumps boost and ends the drive. On F chassis cars it goes on with the first flash, not after the first tow.
• Spending intake money before cooling money. A $430 intake adds sound and a few horsepower; a $400 to $700 heat exchanger keeps the Stage 2 power from fading on repeat pulls.
• Treating ethanol as free power on a Gen 1. E30 is the edge of the stock HPFP. Past it you need a Stage 2+ map and a pump, not a bigger map pack.
• Ordering parts for a 2025 car from 2024 listings. The Gen 3 B58 uses port injection and different parts. Confirm by VIN.

Who This Is For (and Who Should Skip It)

This build order is for the owner who will tune the car, wants it to pull as hard on the tenth run as the first, and plans to stay near Stage 2 with room to grow into fuel: a weekend M240i, an M340i that sees the odd track day, a roll racing Supra.

Skip Step 3 if the car is inspected, still under a powertrain warranty you plan to use, or leased. Skip the intake if you don't care about sound. And skip the fuel step unless you plan to run more than E30 on a Gen 1 or move to a bigger turbo; on 93 octane at Stage 2 the stock pumps keep up.

If It Were Our Car

Gen 1 F22 M240i, F30 340i or F32 440i: plugs, bootmod3 or MHD Stage 1 and the do88 charge pipe on the same weekend. Then the catless downpipe, gasket and Stage 2 on 93, then the CSF triple pass heat exchanger. We'd stop there unless an HPFP is in the budget, because on Gen 1 the pump is the wall.

Gen 2 G20 M340i, G22 M440i or G42 M240i: check the DME lock first, flash Stage 1, skip the charge pipe, then downpipe and Stage 2 on E30 to E50, then Dinan's heat exchanger. On an inspected daily, Stage 1 plus the heat exchanger is the whole build.

A90 Supra 3.0: Stage 1, then the Dinan heat exchanger before the downpipe if the car laps, because the stock car in our blockquote was already pulling timing on track. Then downpipe and a Stage 2 E50 map. On a 2025 or later G20 or G22, we'd wait until Gen 3 parts have more miles on them.

The Hardware, by Step

The B58 hardware list is short. Browse cold air intakes and charge pipe kits by chassis; the B58 options from aFe, do88, Dinan, Injen and Mishimoto are all there. Eventuri intakes are a serious alternative we don't carry.

We are an authorized dealer for every brand we carry, and in stock hardware ships fast.

Shop B58 Heat Exchangers and Cooling

The Bottom Line

Build a B58 in this order: plugs and software, Stage 1, a charge pipe on Gen 1 cars, then the catless downpipe with its gasket and Stage 2 map, then a bigger heat exchanger. bootmod3 claims up to 20 to 21 percent at Stage 1 and 25 to 26 percent at Stage 2 on 93, and our downpipe adds 30 to 40 horsepower with a supporting tune. Intakes are a sound purchase that can go anywhere in the list. Fuel is last and generation specific: an HPFP past E30 on Gen 1, an LPFP and port injection for full E85 on Gen 2. Expect about $2,155 for a Gen 1 Stage 2 street build at our prices, and confirm 2025 and later cars by VIN before ordering anything.

Frequently Asked Questions

What should I do first to my B58?

Install one step colder plugs and flash a Stage 1 map. bootmod3 claims up to 20 percent more horsepower on a Gen 1 B58 and 21 percent on the 2020 and later engine on 93 octane, with no other parts. On a 2020 or later car, check whether the DME needs a bench unlock first.

What order should I do B58 bolt-ons in?

Plugs and software, Stage 1, a charge pipe on 2016 to 2019 Gen 1 cars, then a catless downpipe with a Stage 2 map, then a larger heat exchanger. Intakes are mostly sound and can go anywhere. Fuel upgrades come last and depend on your engine generation.

Do I need a charge pipe on a B58?

On Gen 1 cars, yes, before or with the first flash, because the plastic pipe is a known failure point under boost. On Gen 2 B58TU cars, including the Supra, owners report the factory pipe holding about 30 psi through track seasons, so it is optional on a stock turbo.

Is a catless downpipe legal on a B58?

No. This part is sold for off road and competition use only. Removing or defeating a catalytic converter on a vehicle driven on public roads violates the Clean Air Act, and many states inspect for it. Check your state and local laws before buying.

When does a B58 need fuel upgrades?

A Gen 1 B58 needs an upgraded high pressure pump past about E30, and an LPFP once it heads past roughly 650 to 700 whp. Gen 2 cars run E50 on the stock pumps with a Stage 2 map; full E85 needs an LPFP and port injection.

Does the OneFastShop B58 downpipe fit 2025 cars?

No. It fits Gen 1, Gen 2 and 48 volt mild hybrid B58 cars through the 2024 model year, including the M240i, M340i, M440i, 440i and Supra A90. The 2025 and later G20 and G22 use the third generation B58 and need a different pipe.