The problem on the 2 smoke motor is sustained high speed high rpms at partial throttle.  Full throttle sustained high rpm is better than partial throttle.  It is very hard to set them up to not lean out at high rpm partial throttle.  Inherent issues with a 2 stroke.

If I wanted to run high speed for long periods.. use good gas.. jet main on the fat side. Perhaps use a tune on the fly dial a jet to richen on the fly. Run wide open not partial throttle. Consider a cooler plug. Gear it to run at max torques rpm vs max hp.   There may be better ways. But that is what I have done. Oh and mix oil at 20:1 or 24:1.   Dez would know the better tricks as he runs desert.  Only my .02 and thoughts