A diverter valve, also referred to as a "pop off valve", "blow off valve", "boost re-circulation valve", "air/boost bypass valve" is designed to re-circulate the boost pressure that gets built up in the intake manifold in between shifts. The valve at idle (under vacuum) will remain open allowing the air to circulate freely through the intake to the turbo (s) fresh air side. As soon as the throttle is cracked, i.e.: the accelerator pedal is moved, the valve will be forced shut stopping the re-circulation of intake air to the turbos and allowing all the boost pressure to enter the motor. This non-adjustable valve is designed to be a direct OEM replacement, and includes vacuum hose extension, vacuum hose adapters, and hose clamps. Constructed of a solid aluminum body and brass piston, this valve eliminates common failures with the OEM valves and has large ports for quick response in high boost applications. Boost will come on earlier giving an increase in torque at lower RPM. Also included are two extra springs and two shims for cars using high boost levels. The silver spring is pre-installed and should be applicable for most drivers; it has a spring rate slightly higher than the OE valve and can handle boost levels up to 18psi. The yellow spring is suitable for higher boost chipped applications, 18-22psi. The blue spring is a "race" spring and should only be used in very high boost applications not driven on the street - the high spring tension means the valve only opens for short periods. Compact design does not interfere with engine covers like other valves being sold. Swivel top allows rotation to adjust the hose alignment. Perfect for tight locations as in Audi 2.7T and Porsche Turbo models. Inlet/outlet OD 1.0"/ID .85"