Hi!
Try max 5% nitro, 15-20% all syntetic oil and an Enya 3 glowplug.
Then use a 18x8 Menz wooden prop for best performance (Master A is the worst prop you can use, but ofcourse it doesn't have anything with how your engine idles or how to set the engine).
Are you sure the tank is mounted correctly? Not too high ? And fresh fuel?