Disconnect all vacuum lines and plug to isolate. What is the timing set to? Some Holley based carbs have a manually adjustable secondary to allow more air at idle without opening the primary too far and exposing the transfer slot. What model is the carb? Have you looked down the carb with it running to see if fuel is leaking or running down? Floats could be too high and or too much furl pressure. Electric choke is wire up and working? History of carb?
