As part of your multiple carb cleanings, did you ever pull the Welch plugs and clean behind them? That is kind of the last resort if you have done everything else. We have only had to do that on a couple of Tec engines (out of many) after we have done everything else. Also, HOW are you cleaning the carb? What are you using? Years ago we switched to a small ultrasonic cleaner from HF. We were able to get carbs operating that we were unsuccessful with "conventional" methods (carb sprays and dips).
Michael