all unneeded interior bits (including passenger seat, all trim pieces except for the gauges), replace drivers seat with some form of racing seat would be about 400ish pounds. just going through the engine and replacing all of the nuts and bolts with hardware made of titanium would save easily 100 pounds. then do that with the rest of the cars hardware and that would be approximately another 100 pounds. getting rid of all the sound absorbing material would be about another 50. all unneeded wiring and hardware after completely stripping every bit of comfort or trim pieces out of the car would also save a good chunk of weight. the car wouldn't be really useful for anything but tracking it but it could be done.