This awesome Mach Force XP Cat-back exhaust system produces 11.5 horsepower and 9.5 lbs. x ft. of torque. The Mach Force XP exhaust system is constructed of mandrel bent, polished 304 stainless steel tubing and uses all factory mounting locations for an easy 1hr install time with no cutting or drilling required. This system uses a unique 3" resonance chamber to cancel high frequency sound waves producing an aggressive tone on throttle with a smooth sound at cruising speeds. The elimination of the muffler produces a weight savings of 15lbs. This system comes with a stunning polished 304 stainless steel dual tip to finish off your 135i right.