Cheers for your thoughts, I will have another go at that tune at the club meet next weekend. With the hsn at 4 turns but the difference between loading up and running steady is slight. If I leaned the hsn a fraction I suspect that may give me an easier tune. I have always been running 20% nitro for ease of availability and because of what I was told about engine life and little gain. But know after reading this thread and seeing that the GRP is shimmed for 30% I will be going to 25% this race meet as that is what is readily used by other members at my local club. How different will the tune be and what difference will I notice ie wheel spin, exhaust sound, temps ????