first what type of motor and or car do you have???
but in general you can change the following:
ect... there are so many things you can do, these are just a few suggestions... but we need specifics to help you out, you may want to start with Intake Header and Exaust if you have not already done so.
yeah i knew of those mods... but i was thinking more along the lines of... advancing the timin... intake (i have already done), and thing which i can adjust which i already have to make the car run faster times... not neccissarily getting bolt-ons... i have a JDM b20a, DOHC