Greddy BOV
 

The car I just got recently has a greddy bov (not sure which model), but can someone explain to what causes the high pitch whistle after the PPSHH? Also, what does the adjustment screw.. adjust? The pitch of the whistle? Thanks

adjustment screw should be sensitivity to vacuum, whistle is the noise it makes as the valve closes, even when the turbo is still moving a bit of air.

nothing to worry about.

Ah, I was curious. I actually really like the sound of it, any way I can make it louder?

I don't think you can make it any louder

Their are cone adapters similiar to the hks ssqv which can change the sound. Bigger flange? May let more air pas through assuming its still using the tmic and inlet pipe. The recirculator port is where most people use for thier bov