I upgraded my check valve to the billet pro series check valve after talking with one of UPR's reps. I asked about the difference in check valves and he said the check valve that comes with the kit works great but since I make multiple trips to the track and drive the car so hard and often he recommended I upgrade due to the extened operating time under WOT and boost pressure being over 16psi. You simply swap it out with the original check valve and its roughly $40.