Just got a call from the garage. They said they hooked it up to the fancy thing-a-ma-jig and it appears to be the catalytic converter. He said not to worry, that he would be shutting off the check engine light and let me drive it. Apparently my using ethanol could be the culprit (I'm hoping he's right). I was told ethanol burns hotter and could cause a false reading. I didn't know it was bad for the engine. Granted, a catalytic converter costs $400-500 but is cheaper than replacing an engine or entire car.
SoooOOOOooOOOOoooo...I'll be driving my car like normal and on short trips to my parents until we can be sure it was just the type of gas I was using. He said if the light were to come on again, not to 'freak out' (he knows me all too well). The worst that would happen is that it would feel like I was 'driving with a banana in my tailpipe' and no matter how hard I mashed on the accelerator, the car would top out at 35mph.
Gotta love these guys. We had a flat many Sundays ago (they were closed) and couldn't get the spare tire released. They sent a guy out to us, helped us fix it, and DIDN'T CHARGE US A PENNY. I know, they're awesome. Doesn't hurt that they try to give customers the best deal possible either.