Testing: In testing, the catted down-pipe produced a max gain of +26 horsepower and +21 ft. lbs. of torque verified by our in house dyno. Potential for up to +20 horsepower and +41 lbs. x ft. of torque when combined with aFe's Twisted Steel street down-pipe back (P/N: 49-36330) 3-1/2" to 3" Stepped Design: A unique 3-1/2" to 3" stepped design, is used to increase exhaust velocity and increase usable torque. This means more aggressive throttle response and increased passing power. This down-pipe mounts directly to factory mounting locations and includes hardware for a hassle-free installation. Machined, factory style V-band flanges are used for a secure leak-free seal. 100% TIG-Welded by certified craftsmen for race proven strength and durability. TIG-Welding provides the strongest welds reducing stress cracks. This down-pipe is constructed of mandrel-bent, brushed 304 stainless steel tubing for maximum performance, corrosion resistance and strength eliminating cracking. Twisted Steel 3-1/2 to 3 IN 304 Stainless Steel Race Series Down Pipe w/o Cats BMW M2 (F87) 16-18 L6-3.0L (t) N55 BMW M2 (F87) 16-18 L6-3.0L (t) N55