The wire to the engine temp sensor is broken. Would this cause the engine to NOT pull clean as i gun it?

It sort of misses and eventually cleans out and screams on full throttle.

I did lean out mains from 390 to 270 & leaned clip to 2nd from top.

This helped.

I don't want to lean it out till it blows though.

That broken wire would have nothing to do with the miss. The electrical portion of the engine's performance is on a dedicated coil separate from the other electrical functions of the sled.