Can anybody describe the sound when the diverters are not holding pressure? I have a 04' TT with fabspeed tune, added cold air intakes, ready to install fabspeed bypass pipes, when taking off at any speed there is a loud sound? Kind of sounds like fan pulley rubbing on a metal tube? Had the motor mount replaced not to long ago so I don't think engine is moving enough to rub cold air intake tubes, no indication of any rubbing?? Anybody?

 

Although this doesn't really help, I also have a TT and had noticed the same type of noise for a while. But every time I brought the car into the dealer to try and get it diagnosed, the sound of course disappeared. This was happening when I first bought the car, but eventually is just went away without anything being done. Haven't heard it in 2 years or so, but it definitely is a hard noise to place.