I assume you have not upgraded the stock air box to one of the cold-air intakes available? The stock airbox and resonator do an amazing job of silencing the turbo and BOV sounds. Unless your run the BOV in vent-to-atmosphere mode, you probably won't notice any change in sound with the stock airbox. Personally, I would recommend keeping the BOV in recirculation-mode for best engine performance.
If you don't plan to switch to an aftermarket intake, you could try the "airbox mod" that involves removing the resonator and "tuba" if you want more sound.
