BOV boost pressure relief valve AMAZING SOUND EFFECT !!! Protects your turbo !!! The standard DV valve forces the air into the circulation, while the Blow Off valve - the atmospheric valve lets the air out, which protects your turbo, and at the same time produces an amazing sound effect - characteristic PSSSSSTT !!!! High quality Relief valve Boost pressure BOVNIA AMAZING SOUND EFFECT Protects your turbo !!! The serial DV valve forces the air into the circulation, while the Blow Off valve - the atmospheric valve lets the air out, which protects your turbo, and at the same time produces an amazing sound effect - characteristic PSSSSSTT !!!!High quality