So I see lots of conflicting information on the internet about catch cans and blocking the PCV ports. I have researched for days if it is ok to block the ports or not and have gotten nowhere. So here is my personal experience. I have measured vacuum pressure in the valve cover and the intake manifold vacuum lines with and without the PCV valves blocked and there has been NO DIFFERNCE in my pressures. BUT please keep in mind that my engine timing is off and may effect those readings. Also my catch can at the moment is collecting nothing but moisture! I will redo the test once my new timing chain is installed by DetroitTuned and try to put this puppy to rest once and for all. In the meantime please know that my mechanic says that the PCV ports should absolutely NOT be capped.