I used to have the 306 when all I had done to my motor was just heads and the cam. This last summer I rode in a buddies T/A with the 847 and it seemed to pull like a MF up top, but I almost thought my 306 made better mid range. I'm not changing cams here since I currently have a custom grind for my blower motor, but was just curious which made more power over all. Thanks for the good info.