Well, whatever it may be, the 'Tique is running a bit nicer now. I pulled fuse #11, drained and filled the tranny fluid (it was still pretty brownish, so a good thing to do), and while I was at it, I put in a new fuel filter.
'98 Mystique Zetec w/ auto trans
103,900 miles
Kenwood KDC-MPV7017 CD/MP3 HU
Kenwood KFC-6889ie 6x8" 3-way speakers
'96 Mystique Zetec ATX
108,000 miles