I did every thing you said and it still cuts back at above half throttle. I put a new plug in it i mixed up some Amsoil pro 80:1 and it still does it. I also bought a WA 197 A carb (same as on G23) and it does the same thing. I have the plane in a tail hook on the ground and have been adjusting the carb ,the leaner i get it the worse it gets(cutting back that is) the richer i get it it start to clear up but it cuts the rpms so much it has no power. The thing is it was running great the other day. I'm not sure.

Thanks
smallplanes