Actually, you shouldve beaten that Mustang if youre driving your car properly. Then again, I'm not sure. I know the GS Sport is a good bit heavier than my RS. Based on the weight of an RS, stock for stock, an RS should win. Mustang = 150hp at the fly, RWD so figure in a 20% drivetrain loss and 3150lbs or so. RS = 140hp at the fly, FWD so figure in about a 15% loss, though I've heard 18% and 2850lbs or so. So, based on weight and power, the Eclipse should win, if driven properly. Also, when going 40mph, I've always found its great to blip the throttle and downshift to 2nd. I love going from a 40mph roll. Downshift, grab second, chirp the tires and tear off. Only going to 3rd definitely hurt you.

91 awd: 60-1, 880's, E-Prom, etc.
93 awd: JDM 6 bolt, K&N, full exhaust, Wally 255, otherwise stock.

R.I.P. the original "Factory Freak"
15.5's with short ram and catback only
1996 RS 5-speed