If the looks of the car are of no issue, you could put it on a diet. Removing interior pieces will give you a little weight advantage. If you are the only person to ever ride in the car, and don't care if its a little noisy, take out the back seat, passenger seat, carpet, insulation, headliner, etc. If you get really creative you could find a way to mount the guage cluster without needing the dashboard. Tint the windows and noone can see inside to see what you have done.
I haven't dipped into performance too much for my car so I will leave that question to others.
Welcome to the CEG.
