To help assist the PCV from coming apart from higher boost levels than it was designed for, we have designed an inexpensive billet 8mm check valve to be put between the PCV valve and intake manifold. If you are running a catch can, this valve is to be installed between the catch can and intake manifold. The MPx check valve has been pressure tested up to 125psi and opens at a mere 1inHg of vacuum. This valve comes in an anodized black and has a directional arrow to ensure proper direction of installation (arrow points towards intake manifold source, points away from PCV valve).