Six pack power valve....

The end carbs do have something to do with idle, and each end is different. Do you have Promax baseplates? I have them on both ends, I did them on the front too, didn't like having my hands by the fan. An infared heat gun can be helpful too. Get your ctr carb jet size correct, idle, before moving on to wot. If you can not get your idle down with the ctr carb, one of the end carbs is too rich, and holding your idle up.
Play with it. I still haven't gotten mine completely right, but I am working on it!