Once you start increasing the boost by 8-10+ psi over stock you can start to exceed the functionality of the stock pcv valve in the breather system.
So, what happens is the pcv valve can start to break apart, and fail. This can cause broken pieces of plastic to enter the valve cover/cylinder head, or at minimum you can loose boost, pressurize the head and cause smoking.
So, we have designed a check valve that goes in between the pcv and the intake manifold. This check valve works perfectly with aftermarket catch cans that have silicone or rubber hosing (the factory line cant be used as its too rigid) and should be placed in between the catch can and intake manifold.
Its been tested and proven to hold above 125 psi of pressure with no problems, and it opens under vacuum with less than .50 lb of vacuum. This means it flows well, and resists tons of pressure.
There is an arrow engraved onto the check valve showing the flow direction as well. Because the flow of the pcv gases go from the valve cover to the intake manifold, the arrow points to the intake manifold.