It's been sporadically doing it for a while, but it seems worse now. Plugs have about 100 miles on them. NGK says this plug is okay for this car.
But the more I think about this, the less likely it seems ignition-related to me. I probably didn't describe the problem well enough in my original post.
At engine speeds over 800 rpm, it's as smooth as silk.
When I pull up to a stop, it's fine for about 10 seconds, then it starts with a sporadic miss. That's the only time it misses -- in gear, about 10 seconds after I stop, and it will continue until I either slip it into neutral (rpms increase to about 700 rpm) or I drive off.
It's sounding more like fuel delivery and less like ignition to me. Vacuum leak, perhaps. IAC valve. Throttle body. Low fuel pressure (I doubt this theory). MAF sensor, I guess, but this behavior is very different from the first time it burned out on me. EGR tube/valve. Maybe even an oxygen sensor (I replaced the front bank a few months ago, because the ECU said I needed to -- but not the rear bank). But not ignition.
I don't have it apart yet, but plan to clean the TB first.