First Step First:
GET more Horses First : Increase compression, switch to thiner Gaskit (in close survalance of good alteration mechnic or it will get Valve busted), bore a bigger piston.
Fine Tune Transmission: Modify FinalReductionRatio again you need an expert sitting beside you to decide which set of Ratio would work FITT.
Accelration or TopSpeeed: Focus what you reall desire a top notch Speed or a bullet accelration (I would choose accelration) because we use it in city.
Final Chain Sprocket: change Final transmission Chain Garari accordint to what you need ...
Get Better Air Filter, tune Carb for high performance rather then High economy.
Damn these alterrations its a complete Ocean!