F1 High-Flow Race Headers – Porsche 991.1/991.2 GT3 & GT3RS (T304 StainlessHigh Flow Race Headers Porsche 991. 1 991. 2 GT3 & GT3RS (T304 Stainless Steel) Unleash the full performance and sound potential of your Porsche 991 GT3 or GT3 RS with the Cen Cal Motorsport High Flow Race Headers, engineered for maximum flow, throttle response, and pure motorsport tone. Designed for the high revving 9,000 RPM flat six, these headers transform both the character and capability of your GT3enhancing exhaust velocity, mid range torque,