Actually, believe it or not, I've found that I get better performance with 5% nitro in my ST's. 5% and a #3 plug. And it's the same from my 45 up to my 90. For instance, on my ST 70 mounted on a Katana with a 13X4W prop, I got about 420 more RPM with the 5% than I did with 15%. Both had 18% castor. It pulls out of hovers better, the midrange in the throttle is smoother. As far as the tuned pipe, there are threads on here on building them. Or, you can be lazy and cheap like me and modify an oversized pitts ...