"You're talking about the PCV valve on the dirty side, right? There's no PCV valve on the clean side. Agree you're IM is under vacuum at idle, which should draw flow out of the dirty side, but IN the cleanside, which should mean vacuum at your oil fill if your OE cleanside port was capped, correct?"
Yes, I'm talking about the OEM PCV valve on top of the oil separator on the other side of the engine from the oil fill. I never said anything about relocating it, did I? That part was never modified, and in fact every single part of that is brand new dealer-sourced stuff. The original clean side port had a cap on it from the catch can kit as well because it was replaced by the CSS. I agree, I should get vacuum at idle in the crankcase if the PCV valve (again, on the other side of the engine) is doing its job. With the catch can installed, it was not. It was bad enough that after a few seconds it built up pressure in the crank case and a little air would blow out when I took my hand off.
"I guess I'm still confused why there seems to be air rushing out of the oil fill at idle. I guess this makes even more sense as to why oil might have been getting pushed out the CSS toward the WOT port when under boost."
There's no oil coming out of the CSS at WOT. It's blowing past the turbo seals, most likely at non-boost conditions, because if the crank case is pressurized, the oil will not drain back into the pan properly.
"If I'm interpreting your information correctly, it seems like something is amiss. Maybe you or someone else can give me a sanity check."
Yes, something is in fact amiss. My engine has 130k miles on it, much of them in hundred degree weather in the desert summers of Southern California. As a result, it's got worn rings and a decent amount of blow by. However, the original PCV valve and hose were still able to cope with this condition. The check valve in the catch can kit was not able to cope with this because it is much smaller and will not flow enough volume fast enough. When I switched back to the OEM hoses, no more pressure in the crank case at idle, and no more oil blowing past the turbo seals. The mystery is solved.
