This system produced gains of up to +18 HP and +27 lbs. x Ft. TQ., as measured on our in-house dyno. This cat-back exhaust system is constructed of 3" - 2-1/2" mandrel-bent 304 stainless steel tubing for maximum strength and durability. This system features a high-flow stainless steel muffler, producing a aggressive sound. Muffler finish may vary. Finishing off this exhaust system are dual 4" diameter polished 304 stainless steel clamp-on exhaust tips. The tips features a laser etched aFe POWER logo for a unique style. Utilizing a factory style flange and hangers this system is a direct bolt-on system, which requires no cutting or modifications for a hassle-free installation. This cat-back exhaust system incorporates a factory style exhaust valve which uses the factory exhaust valve motors (not included). The valve helps regulate, direct and control the flow of exhaust gases by opening, closing, or partially obstructing passageways depending on throttle position for maximum performance. A mitered merge collector is used to decrease turbulence and increase exhaust velocity resulting in increased horsepower, torque and improved throttle response.Utilizing state-of-the-art computer-aided design technology, this exhaust system is designed for custom, high tolerance factory fitment. 100% MIG-Welded for race-proven strength and durability. MACH Force-XP 3 IN to 2-1/2 IN 304 Stainless Steel Cat-Back Exhaust Polished BMW M235i (F22/23) 14-16 L6-3.0L (t) N55 BMW M235i (F22/23) 14-16 L6-3.0L (t) N55