Forge Alloy Recirculating Valve available to fit the Impreza 2002+ wrx and 04+ sti Made from billet aluminium, this recirculating diverter valve dumps the charge-air back into the air intake system keeping external noise to a minimum. This increases both quicker throttle response and higher clamping load to maintain boost pressure more reliably. Gives you the sound you want, but keeps the performance! when increasing boost this is needed. The best choice if your looking to make your turbo spool quickly, have your car idle like it just left the factory, and you won\\'t be tricking the mas air flow meter in between shifts, which leads to smoother gear transition handles over 30psi of boost without leaking!