You can modify your ride for either
For appearence only, get front and back lips, side skirts and a wing/spoiler. Replace your stock headlight bulbs with xenon ones, get glow gauges, pedals, shifters etc.
For performance...all you need is an IHE (intake, header and exhaust). And if you are really serious...put in a supercharger or turbocharger with a nitro kit. You will be the talk of the town but your bank account may go broke.