Best perfomance bits Ive done -
Ohilins rear shock
Front fork springs
EBR brake rotor
Rider education - California Superbike School, Conerspeed, Team Pro Motion ART etc.
Once you can get it to turn really well and know what to do you can embarass the crap out of bike wiht more HP all day long.
Having said this , I bought an old CCS Thunderbike XB12 race bike that has been built to the hilt.Its fun ,but ,Im jsut waiting for it to gernade. My lap times @ VIR are a little better on it when compared to my XB9 , but ,not that different. Figure the built bike just spins all the time so Im not able to get the HP to the ground as well as on my 9.