Reading the thread right through, am I correct in thinking that the problem came after changing from debaffled originals to devil cans?
If so, I had a similiar issue but not to the same extent.
I went searching for electrical issues, when it was fueling all along. You have highlighted a significant piece of information in saying that it improves when you crack the choke - to me you have shown it is running lean.
Different conditions and fuel here in Australia, but after shimming the needles .020 and not getting a good result (way too rich - sooty plugs enough to cause misfires on part throttle/cruise mode), I was advised to go up one size on the main jets and put the needle back. Problem solved.
This was another lesson for me to keep it simple and go back to basics as per the Factory Pro website on tuning CV's - mains first, then needles, then pilots. I shortcut based on what I had read here (and my desire to do the least amount of work - lazy combined with if it isn't broken don't f**k with it) and it didn't work.
I am assuming that you have disassembled the carbs and thoroughly cleaned the jets and reassembled making sure that each carb has it's correct jets and base settings? The pilot jets are prone to getting gummed up if left for a time with old fuel.