Your post got me thinking about the CCV once again. The vacuum port between the oil separator and the valve probably is operating at intake manifold vacuum since it controls the FPR on your car.
I cut a quarter section through the oil separator and found there is more structure in the cone than I had thought. There are a series of vanes inside the cone that direct the flow of gases. Also the tube that connects the valve to the oil separator goes all of the way through the oil separator to the hose that drains to the dipstick. There must be some opening in the tube that allows the oil to enter the drain hose, but I have not yet found that.
2001 530i/5 S+P CDV delete/Akebono ceramic pads
M5 SSK/RedLine MTL/M5 rear sway bar/Bilstein HD
BMWCCA Member #337964