with my old GT I removed the back seat and put in some corobu (however the hell you spell it) racing seats in the car, and it made a HUGE difference. Car was definitely quicker, except I started having traction issues. If I would race someone from a first gear roll, the car would go sideways, then spin bad again when shifting into 2nd. and this was in my stock 94...
the rear seat is pretty damn heavy...its at LEAST 40+lbs...every bit of weight helps out. also, installing a tubular k-member and a arms, manual rack, and getting rid of the AC gets rid of 90-100+lbs...............another thing to think about