This has happened on my RB turbos since day one. After an extensive search, it shows on "the other forum" that this issue is related to the oil return line and isn't necessarily bad either.
FWIW, I run on Castrol Syntec 5W-30, no OCC, upgraded RB PCV valve, no oil consumption issues at high boost.
I surmise this issue is MUCH more common than people let on both stock and upgraded RBs alike because not everyone is fully catless. It just has a larger spotlight on RB/ASR turbos because almost all of those guys are catless to begin with.
E90 LCI N54 6AT