Just a quick thought but have you checked the vacuum advance canister? This sure sounds like it is timing related.
Edit...if you suck on it, you should see/feel it moving. Usually it doesn't take a lot of vacuum before you start to notice movement.
I did not, but that’s a great suggestion that I will explore. It used to work, but who knows if it still does.
One thing of note, it sure seems like my BASE timing slipped. It responded very favorably at IDLE to advancing it. (Note: I am not cheating with the idle speed screw, ported vacuum should not be a factor at my idle setting)
That said, I suppose a faulty vac advance probably represents a vacuum leak, and would thusly produce a lousy idle.
