When I ran this hard, still seemed to have back pressure as it blew the oil cap off on one of the two V8 engines I installed these oil catch cans on. The one that worked flawlessly was missing this mesh filter media inside the cap. I blew into both of them and this cap had noticeable resistance. So I removed this filter media from the cap as you see here. No dirt from the outside air can enter the crankcase on this car as one end of the hose vents inside the filter housing getting the benefit of filtered air. The other location has that PCV filter on it. Therefore this is not needed.

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