Here are some links that should be of help:
http://www.brickboard.com/FAQ/700-900/EngineSealsBeltsVent.htm#Crankcase_Ventilation_A_Treatise
Read all the way through this, including the "Oil Trap / Breather Box" section. Pictures of the Oil Trap (aka Breather Box) can be found at: http://www.mikeponte.com/volvo/oiltrap.htm

You will want to clean out all the plumbing for your crankcase ventilation system and the Oil Trap too:
-The tube that croses over the valve cover and connects to the turbo inlet tube.
-The Y-fitting (yellowish plastic).
-The vacuum line that goes from the Y-fitting to the vacuum nipple on intake manifold (may want to replace this small vacuum line).
-Ream out the vacuum nipple with a paper clip and spray come carb cleaner through it.
-The S-shaped tube.
-The Oil Trap, which is located under the intake manifold, near the starter. You will need to replace on oil seal when re-installing it. Go here for more information on that seal and the Oil Trap cleaning operation: http://www.brickboard.com/RWD/index.htm?id=967653

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 268k miles.
'88 Black 780, PRV-6, 149k miles.