If you take a look at the FAQ section for 700/900s there is a long discussion on crankcase ventilation that includes a lot of info on the flame trap and breather box etc. Worth taking a look. The breather box is under the intake manifold, but you can easily attach the hose (which is about 4" long for a 940) from above. On the 740/940 it feeds through between rearmost intake pipe and the next one. The hose fits over a "spout" on the top of the breather box. Just push it on and its done. A little cramped, but only took me 5 minutes last time I did it. The breather box is a black plastic thing bolted to the crankcase. There is a link in the FAQ section to some photos that would help you recognise it. Not exactly sure how similar the 850 set-up is to the 970/940 though. I assume its basically similar. The 200/700/900 series all had the same basic design for the breather box. It is kind of hard to find it the first time, but once you know where it is...... Hope this is of some use. You might try posting on the 850 forum to get a more knowlegable response on the 850 design. Good luck.
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'95 940 Wagon, '85 240 Wagon (RIP), '91 740T Sedan