On the Holley, stamped into the driver's side front surface, should be something like this: "LIST-1850-x" That's the carb's model or list number. Get that first. Is the carb new? If it's over 2 years old, I would rebuild it with a good kit. I like AED myself. Blow out all the passages, and make sure it's cleaned out. Holleys never idle very clean. They like WOT, not idle. The single plane could be hurting you too. You may try borrowing a Thermoquad that runs well. It's one of the best idling carbs anywhere once they are sety up. Also, what distributors did you put in? factpry rebuilt ones, or a new performance one?