B58 Fat Boy 5" Catless Downpipe

The MAD B58 Fat Boy 5" Catless Downpipe is a performance-oriented aftermarket exhaust component engineered for BMW and Toyota vehicles featuring the B58 engine. Constructed from premium stainless steel with smooth bends, it aims to maximize airflow, reduce exhaust backpressure, and consequently boost horsepower and torque. The catless design eliminates the factory catalytic converter, contributing to significant performance gains and a more aggressive exhaust sound. Installation is described as straightforward using basic hand tools. This downpipe is compatible with a wide range of BMW models including the M240i, 340i, M340i, 440i, 540i, 640 GT, 740i, X3 M40, X4 M40, X5 40i (non-LCI 2019-2022), X6 40I (non-LCI 2018-2022), X7 40i (non-LCI 2019+), and Z4 M40i. It also fits the 2019+ Toyota Supra 3.0L. It is important to note that the 2020+ BMW M340i & Xdrive models do not fit the 2025 model year, and specific X5, X6, and X7 models are designated as Non-LCI only. A downpipe gasket is not included and must be purchased separately (Part #18328612538). This product is explicitly stated as not legal for sale or use on pollution-controlled vehicles operated on public roads, highways, or streets. It is intended solely for off-road, race, or closed-course competition use where such modifications are permitted. By purchasing, the buyer acknowledges and agrees that they are responsible for compliance with all applicable emissions laws and regulations. MAD and its affiliates disclaim any liability for improper or unlawful use, and use on public roads may violate the Federal Clean Air Act and similar state laws.