Venturi Drive Super Sound Blow Off Valve - Release Type The all new ribbed main body dissipates heat more effectively and the venturi shaped funnel creates a sharp dynamic sound. Venturi Drive dump valves also feature "Dual Drive" for maximum response, a small port for low boost and a larger port for high boost. The main purpose of the dump valves is to improve the response of the turbo by quickly releasing the boost pressure before the turbo stalls. They are made from die cast polished aluminium with a brass piston and a rubber diaphragm, meaning they can easily cope with boost pressures up to 1.2 bar with the supplied spring. There is an alternative hard spring for boost pressures above 1.2bar and also a soft spring available for very low boost applications. (please see DV Spares) They are also tension adjustable. GT4, ST205, 3S-GTE This kit includes everything needed to install onto your vehicle. This kit is a Release Type