If you think its fast and you're happy with it, I would work on body mods and style it the way you like.
Wheels, lower, new headlights (retro/projectors), tails, exhaust tips, SLP Gen1/2 spoiler, SD front Lip, hood of your choosing, roof rails, etc... lots of things to do body wise to really set it apart

As far as modding and making it faster read both of these.

http://www.grandprixforums.net/ultim...0-a-49055.html

http://www.grandprixforums.net/safel...car-17482.html

Once you've read them completely, refer to the links above and re-read them. You want to KNOW the info before you settle on what to do as far as mods go. And for the modding part, a couple hundred bucks can go along way to making you re-think what fast is in these cars. Stock they are quick for a old grocery getter, but slightly modded makes a HUGE difference.