Assuming that Celica had a 2zz engine (same as my Vibe GT), the "off-the-line-launching" of that engine is really poor (for a sports car). The 2zz is pretty ordinary until it hits "lift" (lift kicks in at around 6000 rpm). When it hits lift, it should get a sudden burst of speed - and eat up any Xterra. (even in "pre-lift" mode, the 2zz engine should have destroyed an Xterra in a race.)

It sounds like your race was over a pretty short distance, and it's possible that the guy never got a chance to bring it up to 6000 rpm. Or maybe that other guy was a piss poor driver and missed a shift or two.

But, I would say that its pretty impressive that a (non S/Ced) Xterra beat a Celica GT.