yep...once the butterfly closes , the charge has nowhere else to go...if you dont run a BOV you will have compressor surge , that is basically the charge hitting the turbo...

but yeah , there are plenty of BOV's out there...they all make different sounds, but most of them have the same basic function. there are different types also , push/pull , atmospheric..etc


and im pretty sure thats an HKS SSQV, or an ARC.