The cylinders are not even close to the same, the 04 is more like the 99-02 ish whereas the 05, 06, and 07 is completly different. I know what you mean on the power delivery, nothing, nothing, then wham, I don't like it either, my son loves it. I would find somebody that specializes in Kawasaki, and see if they have something to give you more low end, might take a pipe, or add to the headpipe something out of the ordinary to get your desired powerband. I tried to have a 310 made out of mine, that cylinder and head are in a box in the attic, it never made 5 minutes without blowing up, that happened twice, there are to many ports and once you punch it out they get to close together.