I think this is the difference.
http://www.600riders.com/forum/fz6-general-discussion/37562-differences-between-fz6-fz6s-fz6s2.html
I don't know if there was much of a horsepower difference but I know throttling and ECU mapping changed a little. In 07 front end plastics, front fender, instrument cluster, swingarm, and subframe assembly changed. I don't think there were any great horse power changes.
Cali model would have something to do with stricter emissions so it might have an extra hose and a can.