Well you can't sub in a breather filter for the PCV fresh air inlet hose that goes to the throttle inlet tube. Seems diameter of the tube on the inlet tube connection meters some of the inlet air. Got a lean LTFT code and a CEL after a few weeks. Watched the STFT move around too much, system will trigger code if trims go more than minus or plus 10 on the fuel trims. Watched it live on my scan tool. So PCV inlet air is back onto the intake tube, catch can has no effect on fuel trims though. Reason for that mod was seeing a little oil in the intake tube ''catch reservoir''.3.6 passes a lot of oil through the PCV system. Catch can on mine catches several ounces of oil and now I just disconnected the air intake for that system from the air box connection as I found oil in resonator box it connects to. Just using a small breather filer to clean PCV intake air. Next oil change I'll see how it is doing.