Hi, Anyone have experience with changing the gear ratio on their bike? How much performance increase will I get? Is it true that due to Noise and Power restriction Regulations, bikes straight from the factory tend to under-perform? I have been looking into getting a 520 conversion kit for my Gixxer since my chain and sprockets are due anyway. eBay has cheap kits avaialble (even after postage from the States) Will I need to adjust my speedo calibration? Is a 'speedo healer' really required?