Find out what the code is.
sounds like they cleared the code so it would sell. then it came back on after some driving. if you have an advance auto parts around you they offer free code reading :waytogo:I got it from a used car lot, so I'll see if they can help me out in the next day or so. Like I said, there doesn't seem to be any change in performance beyond a rougher idle.
Turns out that it's the catalytic converter, although I was also told that it could be because of the fuel used by a prior owner. So, it could have been a lot worse. Now, just a matter of getting it taken care of.