Upgrade your Z4 M Coupe exhaust with the Twisted Steel 2 ½" 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). 2-1/2", 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.