No worries man. Reason I am so insistent is that I dont know you or know how much you know about tuning or how patient you are. Now I know thanks! You are doing everything totally right from the sounds of your post. I had a motor that did exactly what yours is sounding like.

It was caused by a fault in the carb. I would pull your carb completely down and check all the o rings for tears or shrinkage. They can actualyl shrink and not seal properly, this is what happened to mine and it was a very new engine. Also check the carb is seated properly, sealed and tight onto the engine.

If your car is mechanically right (sounds like it is) and your tune is good (also sounds like it is) then a fuel system leak is unlikely (since it is only on this motor). I would start with a carb checkover.