Add power, sound and unique style to your BMW X5/X6 M with this cat-back system which produced gains of up to +20 horsepower and +33 lbs. x ft. torque as measured on our in-house dyno. Dual 3" to 2-1/2" mandrel-bent, brush finished 304 stainless steel tubing keeps exhaust flowing smoothly for power gains you can feel. Designed with a transverse, high flow muffler finished in high temp powder coating for long lasting good looks and unique sound. The factory exhaust valve motor is used to regulate the exhaust flow from a closed-valve, sporty tone to wide-open, aggressive, performance sound. MACH Force-XP 3-1/2 IN 304 Stainless Steel Cat-Back Exhaust w/ Polished Tip BMW X5 M (F85)/X6 M (F16/F86) 15-18 V8-4.4L (tt) S63 BMW X5 M (F85)/X6 M (F16/F86) 15-18 V8-4.4L (tt) S63