Did you say that your best mixture setting is all the way in??
If so, you've got something wrong with your internal carb adjustments/settings.
If I misunderstood that, then check your dizzy for shaft slop. I had an old sloppy one on my 230 last year that worked fine when I was accelerating, but under light loads it would cause a random miss. Changed the dizzy and all is well.
Kirk
