This is a stupid question, and I know next nothing about turbos. I've driven stock S4s, stock Supra Twin Turbo, and a highly modded RX-7 (swapped for a single turbo). I can't hear the whoosh sound when shifting in the S4s. But I def. heard it in the Supra and RX-7. Is this the difference between having a bypass and blow-off valve? Do any newer cars have blowoff valves? Like the Evo VIII and STi?

 

EVO has a recirculating BOV, so you won't hear the "wooosh" as prominent as you would in a VTA (vent to atmosphere) one...

Recirc is more efficient...

 

just put an open air element on, and you can hear the stock BOV. Just as the WRX's...