Question 1

Do I need a tune for a B58 downpipe?

Accepted Answer

Yes. A downpipe changes how the turbo and exhaust behave, and the factory map is not set up for it. Run a matching tune: an off-the-shelf Stage 2 map or a custom tune. We do not recommend driving on a stock map with a downpipe installed.

Question 2

What is the best M340i downpipe?

Accepted Answer

It depends on budget. The VRSF 4.5 inch catted pipe is the value choice. The Active Autowerke GESI and Fabspeed are premium catted options. All three fit the G20 M340i; check the model year for 2025+ cars.

Question 3

Will a Gen 1 downpipe fit a Gen 2 car or the Supra?

Accepted Answer

Usually not. Most downpipes are made for one generation. A few are listed for both Gen 1 and Gen 2 BMWs, like the MST 6 inch, the CTS Turbo 4.5 inch high-flow cat and the Scorpion 5 inch. Spool's B58 race and catted downpipes are listed for Gen 1, Gen 2 and the Supra. Check the fitment line for your exact car, and send us your VIN if you are unsure.

Question 4

Do I need a 6 inch downpipe?

Accepted Answer

Only for big-turbo builds. A 4.5 inch pipe is the normal Stage 2 size. MST sells its 6 inch catted pipe for builds that have outgrown 4.5 inch pipes.

Question 5

Is a downpipe street legal?

Accepted Answer

No. Every downpipe on this page is for off-road / competition use only. None are legal for use on public roads in the United States, including California.

B58 Downpipes for BMW and Toyota Supra

Active Autowerke AFlow Catted Downpipes - S58 X3 M / X4 M (F97/F98)

Active Autowerke GESI Catted Downpipes - S58 M2 / M3 / M4 (G8X)

Active Autowerke AFlow Catted Downpipes - S58 M2 / M3 / M4 (G8X)

Active Autowerke Signature GESI Catted Downpipe - GR Supra 3.0 (A90/A91)

Active Autowerke Signature AFlow Catted Downpipe - GR Supra 3.0 (A90/A91)

Active Autowerke GESI Catted Downpipe - BMW B58N M340i / M440i (2025+)

Active Autowerke AFlow Catted Downpipe - BMW B58N M340i / M440i (2025+)

Active Autowerke AFlow Catted Downpipe - BMW B58 F-Chassis M240i / 340i / 440i

Active Autowerke AFlow Catted Downpipe - BMW B58 G-Chassis (2024 and older)

Fabspeed BMW M2/M3/M4 (G8X) Sport Cat Downpipes (2021+)

Fabspeed BMW B58N Sport Catalytic Converter Downpipe (2023+)

Fabspeed BMW Z4 M40i Sport Cat Downpipe (2019+)

Fabspeed BMW (G20) M340i Sport Competition Performance Package (2019+)

Fabspeed BMW M240i (F22) Sport Cat Downpipe (2016+)

AMS Performance Street Downpipe w/ GESI Catalytic Converter - Toyota Supra A90

Fabspeed Catted Downpipe - G20 M340i