Thank you for this thread, very nice info.
I went ahead and did this same thing to my e46 330xi and I have too much vacuum being created in the valve cover area, I can hardly remove the oil fill cap and I have valve cover gasket leaks developing.
I installed the PCV valve so that the intake can pull as much air as it wants, I was under the impression that this was the correct way to install it.
I believe that you are using this valve to actually limit the amount of air the intake can pull through the valve cover. If so, I have the valve backwards.
Can someone confirm?