Where are idle mixture screws on end carbs set to. They could be supplying too much fuel at idle causing center carb setting to be irrelevant. They should only be barely screwed out from full in. Mopar carbs of course had them leaded up so as not to be messed with unless you really knew what you were doing.

What is idle vacuum, are you certain of no vacuum leaks. Could be several competing issues, not only just 1. Choke completely open?