Are you pulling our leg? You said in an earlier post that the engine ran fine with the return line, except for leaning out with the nose pointed up. Now you say it floods at idle with the return? I'm sorry I do not see how the pump can flood the carb with the return line. Starve with the nose pointed up yes, but no way can it flood a good and well adjusted carb. With the return line in place the pressure to the carb will be exactly that of the resistance in the return line, and we all know that isn't much. Sounds to me like you have a bad carb or pulling our leg.