No, i can tune it to perform. Every few minutes that changes though. And requires tuning. There was a decent thread in the CEN forum, with alot of talk of this. Some guys were working on some fixes. I simply set mine down, rather than get frustrated with it. I could try to dig up the thread, if you wanna check it out.
The only thing along those lines I notced before was the tune changed some throughout the tank of fuel. It was never major, at least not to me, and nothing more than I've experienced with other vehicles with large tanks. The Savage comes to mind.
I do know that the engine and carb have been redesigned for the GST. These changes were specifically made to enhance power and ease of tuning.
I used to have problems stripping 2nd pinion gear. No idea why. I tightened the gear mesh like A.S. says to do and nothing worked.
You're probably aware of the softer gears found on the earlier runs of the Genesis. Even if not, the replacements should have been hardened and not had that issue. Could the issue possibly be that the engine is sitting at a slight angle? That would prevent the gears from making full contact. You may have already considered this, but I though I'd throw it out there.