I am rebuilding a 2002 426 that is in need of a new cylinder, piston, and valve work. I was thinking of going with a big bore kit since it is just a little bit more then reworking what I currently have. Just looking for the pros and cons of 13.5 compression. Do you have to run race gas with this set up? Other mods you could suggest while I have it torn down would be appreciated as well.