ALL THE PERFORMANCE WITH OR WITHOUT THE NOISE!, GFB's Mach 2 utilises GFB's proven TMS Technology to ensure rapid boost recovery on gearshift and optimum throttle response, as well as the ability to withstand boost pressures of 100psi+. Put simply, it can hold more boost than any turbo could produce GFB's Mach 2 diverter valve is configured from the factory for full recirculation (i.e. plumb back, diverter, bypass) venting for the performance-minded who just want the benefits without the sound. Atmosphere venting kits also available. Subaru WRX/STi MY99-00, B4 Legacy, GT/XT Forester MY98-04