It sounds like you are making progress. At least you have some Ideas to keep you busy.
When I suggested to check the full throttle it was just to make sure both carbs are at the same place. Both fully closed and both wide open, just a visual check. If it is too lean it will stumble while moderately accelerating and maybe cruising. You may also need to set the accelerator pumps a little richer. Keep us up on what you figure out.
