My first thought was bad fuel, fuel pump, or clogged fuel filter, then I started thinking maybe an intake Vaccum leak (try the propane trick, it works great!) then after that I thought that with all the tinkering you've been doing maybe somewhere along the line you had a backfire or two? Holleys are VERY sensitive to backfires, sometimes it only takes a small one to trash the power valve, after that they run like garbage until it's replaced. Have all these areas been explored yet?