Concerning crankcase ventilation, flametrap, and oil separator issues, if you are having oil usage, seal leakage, positive crankcase pressure, etc, it might be a good idea to remove the intake manifold and do a direct inspection/cleanup of the oil sep.

My car is an 850 NA 1995, 137K miles. It has had regular care and flame trap has been kept more or less clean. In the last few years oil usage has been up (as high as 1 qt/800 miles during hot summer highway driving). There has sometimes been positive pressure under oil filler and dipstick. One seal blew (fortunately the easiest one - rear camshaft on exhaust side). The oil also has seemed to become dirty quickly after a change. No performance deficits and fuel economy is ok.

I just took off the intake manifold and removed and inspected oil separator. Findings:

The bottom outlet (which should return liquid oil to the pan) was shut solid - had to use a pick to get all the solid crud out. The hole in the block that this outlet feeds into also was plugged completely.

There is an upper outlet which is also open to the crankcase - its diameter is about 1 inch - it was probably at least 50% open - not so very bad.

The 2 small openings on top - one receives the vapor hose from the cylinder head and the other gets the hose which runs back to the flame trap - were both almost completely clogged. This was solid material too - had to remove the hoses and poke thru with a solid wire to dislodge it.

I soaked the oil sep in solvent and lots more stuff dissolved and came out on wash.

In all I would say I removed at least 1/4 - 1/2 cup or more of solid stuff from the oil separator and its inlets and outlets. I took off every hose and elbow to verify it was really clean.

I was under the false impression that if you could blow air thru the flame trap hose or the one on the cylinder head the oil sep should be ok. This is not a good test because there are 4 openings in the oil sep and all of them need to work. This test is also not good because you can blow air through a hose even if it is almost completely clogged.

Removing the inlet manifold wasn't too hard. The leftmost lower bolt (behind the alternator) required (for me) a long thin extension, a universal joint, and lots of patience.

In the course of doing this you can service the EGR valve (if your car has one). For me this was also clogged solid but I could pick the dirt out. And of course you can check all your other vacuum elbows and lines and throttlebody.

I don't know whether this service will end up helping anything - but at least I know everything is clean now.