MAD S58 Fat Boy 3.5" Catless Downpipes
Pipe size 3.5 inch
Catalyst Catless
Application S58 M2 / M3 / M4
Build data

Specs that matter for this part

Hardware

Flow-focused exhaust path

Large-diameter tubing, smooth bends, and a flex section reduce restriction versus the factory exhaust path.

Validation

Catalyst configuration

Catless setup. Review local emissions requirements and product notes before street use.

Requirement

Direct bolt-on hardware

Designed to retain OEM-style fitment without cutting or welding on supported applications.

Downpipes can affect emissions readiness, sound level, and calibration needs. Review the product description before ordering.

With a large 3.5-inch diameter, these Fat Boy catless downpipes free up exhaust flow and lower backpressure, generating a throatier exhaust note and up to 30 HP on a tuned S58 engine. They are built from premium stainless steel with smooth bends and a flex section and fit the 2021+ BMW M3 G80/G81, M4 G82/G83 and 2023+ M2 G87

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