OK, so I've got an oil-separator / filter from a motor factors as suggested by Oddball in this
This is the filta:
It's got 3 pipes:  In (from Cam Cover) +  Out (to main air inlet) &  a little pipe?
I originally thought this small pipe was connected to the vacuum system. Thinking about it, I reckon you could use  to supply the feed to the nozzle under the butterfly in the throttle body. You would then block off the smaller pipe in the cam-cover. See my naff drawing:
Therefore all the breathing (main inlet & small nozzle) will be using filtered fumes.
However, will air just bypass through the filter into the nozzle (as shown in the drawing)???
What do the mig people think of this idea. Should stop oilly gunk getting into the ICV (and inlet manifold too via that nozzle), giving better idle.