i have been seeing many 850s with this problem, especially the turbo ones. but instead of PCV or EGR systems fault, i am looking at other possibility.
why is there oil vapor/ smoke?
possibly because the oil is boiling, right? the temp of the oil could be exceeding 150C, so it starts to boil and cause smoke.
primarily we can say that the PCV is clogged so there is no proper circulation/ suction of the smoke off the engine internal. but what if the PCV is new? and there is still smoke?
so the next step is checking the engine cooling system.
first, make sure that your coolant passage is cleared, especially the thermostat and water pumps. next is the water circulation at the turbo.
then, you can check the engine oil cooler (for turbo only). the hoses on the right side of the radiator. changing oil frequently or changing with oil with higher boiling point could also solve this problem.
mine is 312,000km and upgraded to a bigger turbo which contributes "hotter" oil circulation, but no smoke. neither from dipstick, nor the oil filler cap.
on mineral Pennzoil API SM grade 20W-50 and Mann filter every 5000km.
'96 855GT5 324hp 386lb-ft
Nissan 16V turbo, HKS w/g, SS 2.5" d/p+FGK 3" exh, HKS Evo9 FMIC+2.5" piping, K&N, Apexi BOV, NA cams & t/b, portd head, 5 sub-injctrs, Mocal coolers, AMG 4pot 325mm, AVS 18", Bilstein B6/Vogtland