I removed the SET valve on my Gixxer600. sounded better with no noticeable reduction in power. Many believe its only there for noise reduction as it stays closed below 5krpm, and funnily enough, all noise testing for UK type approval happens below 5k... On the track youre rarely gonna be below 5k, so take it off to save weight. you need to pull the wire from the ECU to extinguish the FI light though, or put tape over it As for the gearing, from what i've been told, all type approval happens at 70mph, so you'll find the bike is geared to keep the revs below 5k at 70mph thus keeping the SET valve closed to keep the noise down... I'm a firm believer that all bikes leave the factory with tall gearing designed for low noise, low fuel consumption and low emissions and to make them less wheelie prone. For the track, none of that is important, so i would start by dropping 1 tooth from the front sprocket and then play with the rear (adding more teeth) depending on the track. Be aware your speedo reads off the front sprocket so changing the gearing will cause the speedo to over/under read.