I've also have a 2002 jetta 1.8t with an injen cai and an apexi twin chamber b.o.v. With the stock diverter valve and stock intake box you could bairly hear the turbo spool up. With the stock d.v. and the cai the sound wasn't the typical pssst but more of a push, like compressed air being released into a metal tube like a pough. I put on the apexi the sound was more of the psst but not high pitched like the f&f sound. Both the stock valve and the apexi valves are loud as hell people from about 1/2 block away could here it and got tons of looks. I say this in the past tense cause now my wife has the car.