Yah, being that it does better with the air screw 1/2 out it is good that your getting a bigger pilot jet. It's starting sound more like a minor detail being overlooked, but I guess nothing is minor when tuning, eh? Look the choke over thoroughly again and also maybe that tube is absent afterall. Maybe the carbs are on the wrong side with each other, is that possible to do that? Hmmm, should be I think, well tube should be in the left carb.