This is going to sound bad but I did a couple free mods when I first bought the car, before I knew much about it and before this website was here. Open exhaust is one of them or at least gutting the cat. The other is turning the boost up. I knew when I left a vacuum line off the wastegate the boost went unlimited so I cut a peice of a Bic pen and put it in the wastegate vacuum line. Then I poked holes in it until the boost was where I wanted it (~17psi). It was primitive but I knew nothing of bleeder valves and it was absolutely free. I also removed the AC in the winter time and spare tire and jack. When the time came for tires I ran the Bowling Greens which at the time hooked better than any dragradial on the street. The only other thing I can think of that made a signifigant difference was sticking a paperclip in the ALDL to lock the torque convertor. It added about 4mph in the 1/4 which is huge for a free mod. Removing the TB coolant lines doesn't hurt but hasn't been proven to help either. If you're good at porting, you can do the intake and heads which makes a very big difference but isn't totally free. Porting the exhaust elbow on the turbo is free and it takes about 45 minutes to do. I was on the stock fuel pump and regulator with no scan tool because I didn't know any better at the time, I guess I got lucky but I did manage to go deep in the 13s like that.