Assuming you have the high speed needle set correctly, do the "pinch test" while idling. Pinch the fuel line closed. If the engine momentarily speeds up then dies, your low speed needle was too rich. If it dies right away, then it could be correct or a bit lean.

Another sign of a too rich idle is if you suddenly "gun" it from idle and it stumbles, it's too rich at idle.

I had a TT .46 Pro which I had a devil of a time keeping running. All my problems went away when I changed from 5% nitromethane to 15%.