Ok, few things. My friend owns an 04 600RR with PCIII and exhaust. He played with a Z06 and beat it on a roll. The owner said "It's got headers, H pipe, and a little something special." My friend heard no whine so we're guessing some NOS. This was a Z06 which has more power than most wrx's, except maybe some stage 4s. Aerodynamics, from what I've read, don't really hurt bikes until a bit over 100.
Second, a shelby cobra with a 427 might have crappy aerodynamics, but my family and I have a shelby kit and it weighs 1800 pounds. 1800 lbs + 400+hp = very fast quarters. I gaurantee that power:weight ratio would overcome that wrx in a quarter. And I would put money on it.
My guess is he didn't realize you were about to hit it and was in a higher gear than his power band (I've made this mistake on my bike). So he saw you hit it, had to downshift at least once, and then was playing catchup. Go on the supra forums and check out their races against bikes. Most people need around 4-500 hp to beat a 600 from a roll.