If the engine runs fine from idle to mid-range, then quits when you push full throttle, it sounds like it's much too lean to me.

If it was too rich it wouldn't "peak for 2 to 3 seconds" before it quit. What's happening is it peaks for a short time, then because it's too lean, it overheats expanding the piston causing it to cease. (NOT a good thing!)

I'd try richening the top end by at least 1/2 to 3/4 turn.