Greg,
another thing to consider is the fuel your using. Engines from a far where nitro is on the high dollar side tend to need either VERY little nitro, or even none at all. I've had GMS's, MVVS's and even Norvel's act crazy with too high of nitro fuels. They act is if your are chasing the needle, and never can find the right setting. When you use too high of nitro for a given engine, it makes the needle settings become critical.

I don't know if this is a factor in your case, but it is good for one to know and I hope it will help.
Dennis