An Alloy Atmospheric Dump Valve to fit the Subaru Impreza 2001 onwards models including the 2009 GR STi .
 
Made from billet aluminium and hand polished in the UK, this atmospheric diverter valve dumps the charge-air to atmosphere creating the "Whoosh" sound most commonly associated with rally cars when the throttle is lifted. This increases both quicker throttle response and higher clamping load to maintain boost pressure more reliably.