My ASP .91 runs fine one FAI (0%) fuel and 5% nitro. But with 10% it detonates, runs hot, and quit once, if not running a much richer setting. With 5% and less it is very user friendly except setting the idle is a bit tough with FAI fuel. With 15% or higher I wouldn't be surprised if it would act as you describe. You may have damaged it from running high nitro fuel.