I waited until mid-afternoon before hearing from you on what "Check Engine" light was for - still don't know for sure, so let's talk about it - some more: reset light? no, not to have it 'go off again' a short time later but I just spent >$100 for an oil change that I didn't need and the damned light is still on. Cat Convert replace: huh? - just passed inspection w/in last month - w/ flying colors - just as before; so is the recommended replacement based on miles (156K), measured exhaust, or what?