I should update the symptom list. It seems to happen any time now, not just when warm.

Just wanted to give an update on this. Seems that I've got it mostly nicked.

I tried the following items in sequence because I had the swap-out parts (thanks Rick!) or would be replacing the items for my swap anyway:

-Swapped ICV (Because cleaning the first ICV with carb cleaner changed the symptoms briefly)
-Swapped Air Flow Meter/Fuel/Air door
-Checked plugs: All had a thin layer white material caked on them indicating a lean mixture.
-Replaced fuel filter (at 170k, it was due anyway)

Nothing was helping and I was starting to wonder what I was going to do next. Everything else was going to cost more significant $$$ and I'm just about to swap the motors out so I was about to give up and just keep driving it. Then I remembered my donor M3.

I walked over to the parts pile, unbolted the O2 sensor from the exhaust and brought it over to see if it would match up to the ti. Sure enough, it fit.

The start was a little rocky, but I staved off disappointment as I knew the computer would need to re-adjust to the new O2 sensor if that was my problem. I took it out on the interstate, and low and behold, no more check engine light.

Ran around on surface streets, and everything had smoothed out. So the major culprit has been sorted.

There is still a problem with hesitation and bad idle when the car starts warm, but as soon as I get rolling (1/2 block) it's back to normal, and still no CEL. I suspect that the borrowed ICV valve I swapped in may be sticking (I should have cleaned it before swapping it in). Once I swap the original stuff back in we'll see if it clears up.

Thanks to everybody for the ideas, and thanks to Rick for letting me raid his spare parts bin for my investigation efforts!

Glad to hear the good news, Robert. We need to grab another beer sometime (preferably somewhere with a little better scenery than Hugo's ). Oh it's Chris from Autohaus btw.