I have three ST 90's running like a charm. Two are in cowls on a twin so I can't check the needles, but the third is set as follows: 14-6 prop, 10% nitro, 18% oil in the fuel, muffler pressure, high speed needle 1 3/4 turns open, low speed needle 2 7/8 turn open. Needles checked with throttle barrel fully open.
Chuck