I have recently been through all sorts of crankcase vent issues with my 1994 850 and can, I hope, provide some useful advice.

The oil rings on these cars appear to wear faster than the compression rings. This leads to some oil use later in life but should not lead to serious problems. As the get oil vapor in the crankcase it comes through the crankcase vent system and flame trap, mixed with the induction air and burned. This oil vapor attacks the plastics and rubber used for all of the components of the crankcase vent, including the 'fresh air' inlet where the air from the air box and the crankcase vapors are mixed. This is why your flame trap has a hole in it.

The holes in the flame trap and the size of the aperture in the flame trap fitting in the 'fresh air' inlet play an important part in regulating crankcase vapor pressure. I recently replaced the 'fresh air' inlet (about $50) and have seen a noticable decrease in oil consumption.