I haven't had a chance to test the blow-off valve sounds with the new update, but does it depend on what view your in? If it's more realistic, then they should easily be heard in the interior view. I drive an SRT-4 with a Mopar BOV, and I can EASILY hear that from my interior. Now I know the stock cars in the game may not have aftermarket BOV's, but if they're going to make them loud on the cars with one update, and then quiet it down on this one, it shouldn't matter if they're considered aftermarket or not. Same thing with replays. If the car is coming at you, then you should easily be able to hear the BOV.