I like Nibbi as well. I have 2 on 2 different motors and they both perform flawlessly.
If the breather port on the valve cover is breathing, then nothing to do there. I don't have any hoses on mine and they work fine, no drips, etc.
The white smoke/oil burning thing is a mystery (at least to me). I've never seen/heard of a carb that has no oil connection to it have influence on oil burning or creating a white exhaust output.