That's what it was - bad plugs. I checked the records and saw that they hadn't been changed in at least 10 years. I pulled them out and they were white at the ends (previous owner had timing out of whack).

Eight new NGK BP5ES spark plugs later and she's running like new again. I also cleaned out the ICV with some brake cleaner and it seems to have resolved the wandering idle issue.

Thanks for the help!