ORIGINAL: Not24
I'm sorry to hear that. My engine, after only 16 oz of fuel, will transition faster than any servo can move the throttle. It can go from a 2500 rpm idle to wide open as fast as you can move the pushrod. I found this to be simply amazing. That is with the stock muffler and glow plug, an out of balance wood 14-6 Zinger, and 15% Omega. I'd suggest increasing your nitro to 15% before condemning the engine.
With nitromethane costing $100 a gallon around these parts, there's no way the average modeller can afford to feed an ST90 fuel with 15% nitro in it. Besides which, the prevailing wisdom is that the STs prefer *low* nitro fuel.
Maybe we should try unbalancing the prop? :-))))