I have seen bad air leaks cause this as well. I would not concentrate on the wiring.....Yet. Since you switched them. If you have the means to do a leak down test, do it. If not, you may want to look at Docjwatson's Thread on making a tester setup. Double check your airscrews and all the jets, needles, slides, etc. and make sure they are all the same and make sure, again, your pilot jet on that side is not clogged. I have put squeaky clean carbs together to find I had debris in the can of fuel I purchased and clogged up the pilot immediately. Just pay attention to the what is in the bowl, etc. while you are looking everything over. Make sure the slides are in sync.