eg: HKS BOV is designed not to leak boost when under load an it releases all the pressure through the bov, it keeps the turbo spooling because its not plumbing back.
Standard plumback. the standard r33 gtst bov is designed to leak an it plums the pressure back through the turbo ? which causes the fins to chop it up an it slow the turbo down. (lag)
correct me if im wrong!!!