just to add my 2 cents in my oponions. I use to have a 1997 Ford Escort LX (not a ZX2) that i dragged at the local track. The factory drivers say that my car should be doing a 1/4 mile in about 18.1 seconds, but i sayed no and dragged against a lot of cars. One of which being a ZX2, which i beat (i bet he was a little upset

), and i dragged against a truck that was running with a 17.1 time slip and beat him easily, a couple of times. I never actualy got a time slip, but figuring the car was doing around a 16.3 or so 1/4 mile. So with that said, the best way to describe why the big differences in times is the the boss must have been looking over the workers shoulder when they put that one together!! hahaha, but seriously, every car is tuned ever so slightly different.
Whew, sorry about the overly long post, but i was given a lot of crap when i first said that i was doing 15.9-16.3 sec. runs, so I feel all ya that have been given crap!
peace