Carl-
Fouling at low speeds and/or starting and stopping looks to me to be either your air screws, slow jets or needle clip position. I'm writing off taper and cutaway as you didn't change anything, and the main jets don't come into play until 1/2 - 3/4 throttle minimum. With the Uni & 4-1 being your exception to stock, both will probably flow a little more air than OEM, which would tend to lean things up some, unfortunately the opposite of your problem.
First, assuming your near-stock configuration, I'd go back to stock settings on the air screw: 1-1/2 turns out +/- 3/8. Then I'd also check your clip settings for stock (4th groove from the top), as you never know if they're on the right slot or not.
The stock slow jets are #38, which is a mighty tiny hole. I also just read a thread indicating they have a small venturi-shape within, which may have been buggered up in the cleaning. Or the whole thing may have been reamed out. I don't think there's any going back here - gotta get new ones if they're trashed; BUT, I don't know how to check these either. I like the idea of a nylon bristle, but that's too late for this thread.
A last thought is to check your float settings (22mm), , I seem to recall that if it's too high, you may flood the jets and suck way too much fuel. I would expect them to wizz some fuel when it's off and the petcock left open if it's that high though.
One foolish last thought - is your air passage open, the one in the tool-tray? I used to keep some stuff in there that would sometimes shift and partially block the screen. And when I bought it, the screen was gummed up; an hour with a toothpick solved that one. And now it's just a couple of tools allowed in there.
