I just got a 2003 Nissan Altima S, I want to sup it up but i don't know where to start?

well, where do you think the car falls short? if it doesn't handle so well, lower it and stabilize it. if it's a lil sluggish feeling get an intake and exhaust to start.

I have a 02 3.5 se. I did an intake, eibach pro kit springs, stillen sway bar, Mossy cat back exhaust, 17" G-racing Mitos, dash kit, shift knob, custom rear spoiler,35% tint and JDM clear headlights.

you been to the track with it yet?