I have an MDS 78 that has similar issues, and I just got tired of dinking with it. Not quite as bad as yours, though . . . it would idle great, and run full throttle great, but if you tried to stay at mid throttle for any length of time, it would load up and die. High needle didn't have any more room to lean without going too lean on the high, and any leaner on the idle needle and the idle wasn't stable.

So, I spent a few bucks, threw a Perry carb on it, and it's perfect on the test stand now . . . one of these days, I'll get it
into a plane again . . .

- Tim