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.