Steve:
There's something else going on with Matt's 33GT. We even went to a different brand CDI unit it on the assumption that the stock CDI had some sort of minimum RPM code built into it. It really just acts like a fuel draw problem, my theory being that those 4reeds need more negative pressure than a typical 2 reed setup, possibly because their individual surface areas are relatively small, though their combined surface area is probably larger than a comparable sized engine's 2 reed system. Matt's engine behaved well for the first 3 or 4 flights, then became a problem. We looked at various possibilities, leaks, warped reed block and the like, and it really didn't solve anything. It will be interesting to see what comes back from the repair.