BMW M340i/M440i xDrive B58 Catted Downpipe - G-Series G20 G21 G22 G23 G26 - 200 CPSI Heat Shielded High-Flow Sports Catalytic Converter, 4.5-inch Stainless Turbo Downpipe Performance Catalyst Exhaust Upgrade

Unlock flow, sound and heat control on your G Series B58

Give your BMW M340i or M440i the breathing room it deserves with an insulated 200 CPSI performance catalyst. This catted downpipe features a large 4.5 inch canister and robust stainless construction with an integrated thermal barrier that helps contain radiant heat and keep underbonnet temperatures in check. Expect sharper turbo response and a richer, deeper exhaust note while maintaining a catted solution that suits fast road builds and tuned B58 setups.

Why enthusiasts choose this upgrade

• High flow 200 CPSI cat for reduced back pressure and improved spool
• Thermal shielding to help manage heat soak and protect nearby components
• Heavy duty stainless fabrication for strength and long term durability
• Oversized 4.5 inch body to support increased airflow on remapped cars
• Direct fit for G Series M340i and M440i with the B58 engine
• Delivers a fuller, more aggressive soundtrack without going catless

Real world results

We have fitted and run this catted downpipe on customer M340i and M440i builds. Feedback has been consistently positive, highlighting the deeper tone, smoother power delivery and noticeably better heat management around the turbo area. It is a popular alternative to decat pipes for drivers wanting performance gains with a quality catalyst in place.

Fitment

Designed for BMW G Series M340i and M440i models equipped with the B58 engine. If you would like us to confirm compatibility with your specific chassis and build, get in touch and we will be happy to help.

Professional installation

We recommend expert fitting for the best results. MJ Modifications offers installation at our Warwickshire workshop. To request a quote or book your slot, email info@mjmodifications.co.uk.

What is included

• 1 x insulated 200 CPSI catted downpipe with 4.5 inch body in stainless

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