Hello!
well to me it sounds as if you have to set the idleneedle a little leaner!
The pinch test is not that precise...I'm not using it and no one I know off in pylonracing uses it.....much better is to listen to the engine and respond to it ....this takes a little practise but is really easy!
If the engine ,when you give full power from idle (you could wait 10 sec or some minutes ) sputters, hessitates and belching raw fuel out the silencer.....then the idle needle is set too rich ...and you better screw it in some. How much you turn it in you have to deside yourself but experience will give you knowledge, try half a turn!
Then do the same thing again: idle the engine for half a minute and then give full power, the engine should react at once without hessitating.
As for idlebar plugs ! They are a thing of the past ! Use a good sport plug as a Enya 3 ,OS 8 or a Rossi 3-4.
Fuel 5%-19% nitro .