There are 2 parts to the PCV system. We have the check-valved vents that lead to our intake manifold, and we have the open vents that lead into our intake tubes.
I am not entirely sure why the intake manifold fed PCV vents have a check valve since the car is non-boosted from the factory.
During high vacuum at idle and such, the manifold vacuum should be pulling so much through the PCV that the air filter tube side of the system is probably pulling fresh air IN.
With both my 350z and my 370z TT setup, I kept the stock PCV system. Under boost, the PCV check valve should shut, and the only ventilation for the crankcase would be the air filter tubes.
What I only just NOW considered thanks to this thread, is that running a "stock" style PCV system in my 370z TT is causing a problem that I hadnt thought of. The difference is, my 350z was a MAP (speed density) EMS system. My 370z is not. During high vacuum idle, my PCV system should be drawing fresh air through thru my air filter tubes. So I have an un-metered air source entering my engine at idle, since my MAF sensors are just before the throttle bodies.
Huh... thank god for closed loop feedback I suppose.
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