This catch can runs inline with the PCV (positive crankcase ventilation) valve and retains it s factory function. When the intake manifold pressure is close to or greater than atmospheric pressure, the PCV check valve closes and, thus, this hose experiences no flow. Conversely, the PCV hose 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. Note: Because the Radium catch cans are pressure sealed, they are great for boosted applications as well so intake manifold connection is permitted. The kit installs in minutes and is easily removed for servicing.