The car trouble (and the associated ride-the-motorcycle-in-good-weather, hitch-rides-in-bad-weather) must be getting to me. It's low-level stress, but it is still stress.
I had a dream in which I discovered I'd somehow driven off in someone else's car, an everything was broken.
Anyway, Manifold-Air-Pressure sensor doesn't fix the engine misfire. Neither does cleaning the Idle Air Control Valve.
It's possible (remotely) that the problem is somewhere in the ignition system. Since the ignition coil pack, spark plug, and spark plug harness are all less than a month old, I doubt it. (Unless I set the spark-gap wrong, or somehow cracked a plug such that it never fires...)
I'm spending an evening on this problem again, and scrounging around for a secondary vehicle...
UPDATE: after a chat on the phone with a car mechanic (a relative of a friend from church...and 'the car guy' who is considered a good source by people who do lots of their own car work), I hit on a different pathway towards the problem.
The cylinder misfires were on the same coil in the Ignition Coil Pack. The problem could be ignition.
I pulled the spark plugs that were misfiring. One plug was fouled in a way that looked it was not firing.
I looked again at the Ignition Coil that had been replaced with the spark plugs and wires. Either the problem was in there, or the problem was in the timing signals reaching the Coil. I decided to test the wires providing the timing signals, and then test the Coil itself by switching back to the old Coil. The first test fixed nothing (but I was just moving the wires, looking for a weak connection). The second test fixed the problem.
Weird. It is remotely possible that I quoted model year 2003 instead of 2002 to the sales-clerk while purchasing the Ignition Coil. Is the difference enough to cause trouble? Or does one of the pins on the new coil have a size variance that can cause trouble once the engine warms up?