BMW B58 Gen 3 (B58TU) 4-Inch Decat Downpipe | M340i M440i M240i GR Supra Z4 M40i – Midnight Performance

Midnight Performance™ BMW B58 Gen 3 (B58TU) 4-Inch High-Flow Decat Downpipe

Unlock everything your twin-scroll B58TU has been hiding. Our 4-inch T304 stainless decat downpipe completely eliminates the factory catalytic converter — freeing exhaust flow, accelerating turbo spool, and giving your B58 the sound it deserves. The essential first step for any Stage 2 build on the Gen 3 platform.

Why Choose Midnight Performance?

• 4-inch (101mm) straight-through bore — maximum exhaust gas velocity from turbo to cat-back
• Hand-finished, back-purged TIG welding — structural integrity under track-level heat cycles
• CNC-machined flanges — precision alignment, zero leaks
• Dual pre-positioned O2 sensor bungs — factory-spec bung placement for seamless sensor integration
• High-dampening flexi joint — absorbs engine movement under launch control and hard downshifts
• Aggressive B58 acoustics — turbo whistle, exhaust crackle, and a deep inline-six roar at WOT

Technical Specifications

Verified Fitment (Gen 3 B58TU Engines)

• BMW M340i / M340i xDrive (G20/G21): 2019–2026
• BMW M440i / M440i xDrive (G22/G23/G26 Gran Coupé): 2021–2026
• BMW M240i / M240i xDrive (G42 Coupé): 2021–2026
• Toyota GR Supra (J29/DB Chassis — B58 6-Port): 2020–2025
• BMW Z4 M40i (G29): 2019–2026

⚠️ Off-road and track use only. This decat configuration deletes the factory catalytic converter and will not pass a standard UK MOT emissions test. Not for use on public roads.

Professional Fitting Available in Birmingham

Our workshop team can install this for you. Contact us to book your slot.