Mike,
You may want to call these guy's and talk to them about your problems if you really think it is carb-related. We know you don't want to spend any more money but you might be able to ship the carb down to them in Ontario, California. I have not used them but I have talked to guys that had problems, called them and bought the carb that corrected the issues. Maybe they can do something on existing? here is their website
http://www.customcarbs.com/Home.htm