Ok folks, here's the latest.
I was able to test the pins #9/5 with the multimeter again - this time on AC volts. Number that came back was about 90v. Not sure if that's telling or not - not sure what a healthy measurement would be.
The big news came when we took the carbs back off the bike, quadruple checked the tiny port holes that travel from the idle jet towers through to the throat of the carbs. All showed clean, with clear passage of air being felt distinctly from the 2 smallest holes behind the butterfly. Both holes in both carbs seemed clean. The air/fuel screw passage was already fine.
I had purchased the rubber plugs that insert into the idle jet towers because they had been missing, but when we thought back to our initial testing - all the best results seemed to have been without these plugs. We decided to test the bike with the 90/120 jets, clean passages, and no rubber plugs. The issue was gone immediately. While the tuning could be a bit better, at this stage it seems that a slightly larger jet could do the trick. Air/fuel mix screw helped to a point, and then we ran out of comfortable adjustment room.
So this doesn't sit well with me - getting the right result from the wrong reason... But at this point - it seems like it's worth trying under load. The irony that we finally get the bike fat a place woth road testing again during a snowstorm is not lost on us
I'll update when I get a chance to fire her up on the road...