I was in the exact same situation and I decided to start with the HJR 4mili Dune/Hillshoot port. The motor is amazing and I have run it with zero problems for 2 summers now. My setup is: Shearers, 35mm PWKs, Chariot Intake with Boyssen Reeds, and Noss Head. The quickest unit I have run against was a mildly built Honda 450 dirtbike that was close on the gravel but not so on pavement, giving a fairly big edge to the banshee. At aroumd est 75hp it pulled very hard, but the power is so addictive that I since upgraded to a ported 421 cub with 39mmPWKs that I hope with all I've read, will be close to 100hp... should be able to notice that. I will also keep you guys update on how it runs after it is tuned!