One thing more to check is where the tubes from the oil separator go to the turbo input. It is possible there is a blockage on the corrugated input pipe where all the smaller tubes enter, especially the tube from the oil seperator. Son-in-law discovered it on his S 70 and recently I was redoing a head and vent system and checked. This area was nearly blocked.

Anyway, check it out before you blow a rear main seal.

dick