O.K. guys this is my first post so please do not kill me. I race the vet class and the elevation that we race at is around 3000 to 4000'. I just put the Dr. D system on my bike and it seems to run pretty well. There is a substantial difference in power from the stock pipe. My question is about jetting. I did not change a thing from stock. I backfires when I let off the gas. Do any of you have this same setup and what elevation are you riding? Please advise. Should I do some jetting changes?