The PCV system consists of a liquid vapor separator inside the cam cover and a restrictor built into the idle speed air distributor - a plastic junction block located between the head and fuel distributor.
Under manifold vacuum conditions clean air flows from the air cleaner housing to the cam cover nipple, through the engine and into the idle air distributor. Flow is limited by the 1.5 mm restrictor built into the idle speed air distributor.
Under low manifold vacuum conditions the flow can reverse.
Recommend you remove the idle speed air distributor and associated hoses and throughly clean them out. If this does not solve the oil in the air cleaner problem it might be the liquid vapor separator, so you will have to remove the cam cover and check it for clogging and mechanical integrity.
If the PCV system is functioning properly and the engine does not have excessive blowby, you should only get, at worst, a light film of oil in the air cleaner housing near the nipple, but there should be no liquid oil.