There is a separate flange mounted on for the Greddy, so all you do is bolt it on and adjust it till you get the perfect non-stalling/turkeyless/whistling sound combo. Don't let anyone tell you there is no purpose to a BOV. See, when you are accelerating the TB is open, and the turbo is spooling up and pushing air to the TB. When you suddenly let off the gas to shift, the TB closes and the turbo is still pushing the air to it. That air has no where to go so it goes back toward the turbo and causes "cavitation" of the air forcing against the turbo. This will cause unnecessary wear on your turbo. Also, when you shift quickly you want the turbo to run efficiently. The BOV lets that air the turbo is pushing out to the atmosphere, and your turbo stays "spooled up" so when you hit the gas after the shift it is not slowed down by all of the backpressure. So there is a safety and performance plus to having a BOV. The reason you don't hear the turkey on the stock car is because when you put an aftermarket intake on your car there is more air being easily used by the turbo, and thus there is more potential backpressure. Now, the reason people use a dual BPV/BOV setup (including me) on our cars is this: our stock computer is setup to "think" the car is using a BPV, which basically does the same thing as a BOV except it diverts the air back to the intake after the MAF. So, our car believes that air is going back to the intake. When people use just a BOV, it is going to the atmosphere only. So there is less air going in than the car believes, and thus more fuel is dumped. This causes a stalling when your car goes from revved to idle. People have come to a happy medium by using the dual setup. This gets the best of both worlds. I do not stall, I really have to abruptly shift to get any turkey sound (and it is barely audible), and my Greddy BOV sounds awesome. Hope this helps.
