I too believe that you are lean on the low speed needle. You all should give the 15x4W APC a try. When I had this engine on a .60 Cap 232 I was getting 9200 rpm on a 15X6 APC using 30% heli. The 15x4W should be ballistic then. Also don't be afraid of the higher nitro fuels. Satios love nitro and anything up to 30% will not hurt them.