Upgrade your Z4 M Coupe exhaust with the Twisted Steel 2 race pipe. Mandrel bent from 304 stainless steel tubing for maximum exhaust flow and corrosion resistance, the mitered merge X pipe eliminates drone and maximize scavenging. This system delivers gains of up to 13 horsepower and 20 lbs. x ft. of torque when tested with PN 49 - 36339 exhaust and are 100 hand TIG - welded for strength and durability. Includes high quality gaskets and is a direct bolt - on system for a secure, leak - free installation. In house dyno testing produced gains of up to 13 horsepower and 20 lbs. x ft. torque (tested with 49 - 36339 exhaust). 2 - 12, mandrel - bent, 304 s tainless steel tubing for maximum performance, corrosion resistance, strength, and durability. A mitered merge X pipe is used to balance and evenly distribute exhaust pulses traveling through the exhaust system, minimizing exhaust drone and maximizing scavenging. 100 TIG - welded by certified craft smen for race proven strength and durability. TIG - welding provides the strongest welds.