These engines come from the factory with no diverter valve of any kind, resulting in turbo compressor surge every time the throttle is closed after boosting., , The intake is acoustically tuned to surpress the fluttering sound of compressor surge, it does not eliminate the effect of pressure pulses- that is what diverter and Blow off valves were originally designed to do., , The GFB T9430 re-introduces a blow-off valve into the 1.2/1.4 TSI system, which eliminates compressor surge to protect the turbo, and delivers the signature blow-off valve "whoosh" when liftingoff the throttle.