The PCV catch can kit runs inline between the PCV valve and the intake manifold and promotes clean filtered air back into the engine. When the intake manifold pressure is close to or greater than atmospheric pressure, the PCV valve closes, and this hoses experience no flow. The PCV hoses will experience metered vacuum when the engine is idling, steady state cruising, and decelerating. This would normally draw unwanted crankcase vapor, unspent fuel, and oil sludge into the intake manifold immediately after a high load run.
