MAD B58 Fat Boy 5" Catless Downpipe
Pipe size 5 inch
Catalyst Catless
Application B58 BMW / Supra
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.

The Fat Boy downpipe is an oversized 5-inch catless system that delivers unrestricted exhaust flow, reducing backpressure and unleashing noticeable horsepower and torque gains. Made from high‑quality stainless steel with smooth bends and a flex section, it provides a direct bolt-on fit for BMW M240i, 340i, 540i, 740i, X3/X4 M40, X5 40i, X7 40i, Z4 M40i and Toyota Supra

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