G8X M3 / M4 4" FATBOY Midpipe – Flow Is Everything Flow is everything and the new MAD 4" FATBOY Midpipe delivers exactly that. Designed specifically for the G8X M3/M4 platform, this midpipe is built to maximize performance and sound without compromise. Featuring a full-length single 4" center section and a minimum pipe diameter of 3" throughout, the FATBOY Midpipe is all about maintaining optimal exhaust flow from front to back. Expect a deeper, more aggressive tone with significantly less rasp, even when paired with aftermarket downpipes. Whether you're pushing the limits on track or just want that perfect balance of refined aggression on the street, the FATBOY Midpipe transforms your G8X's character in all the right ways. Key Features: Full-length single 4" center section Minimum 3" diameter throughout for consistent flow Deeper, more refined exhaust note with reduced rasp Perfect pairing with aftermarket or stock downpipes Includes 3" and 2.75" reducer couplers to connect to 3'' aftermarket axle-backs such as ours or factory axle-back systems Utilizes Oem Cut location and clamp design for easy installation and reversibility