270 miles later ... there is the smallest trace of oil in the reservoir hose, the transparent tubing has some light oil (yellow) coloring and there are maybe 4 to 5 drops in the cap (Bottom of the hose). So the system is working EXACTLY as intended. Crankcase breathes, oil deposits in the discharge hose.
Engine does seem smoother, particularly at slow speeds. At higher speeds its the same.
Power seems better. I even touched the rev limiter twice today as I was ehem ... testing with a buddy on his Concours 1400.
I'd recommend doing this mod to the 990. I see no downside. Particularly if you like to service the bike yourself, it's going to be unbelievably easy to remove the accumulated drops of oil from the discharge tube when you are changing your own oil/filter.
If there is interest, I can do a "How to do it" but it was covered in 2008/2009 so the forum has enough pictures, diagrams and explanation that even I could do it. By myself. And I'm not that smart.
Oh, and no traces of oil whatsoever on the frame, TB's or MotoHooligan box.