'85 3.2 won't hold idle on re-start

[jlex]

I've been chasing this problem for a while. Maybe someone has a solution.
My 1985 3.2 engine starts great, drives great, etc. HOWEVER; if I drive it somewhere, like a movie, or concert, then get back in it 2 or 3 hours later, it's tough to start (cranks okay), then once it gets going if I take my foot off the accelerator, the RPM's will go so low it will stall out. I'll need to restart it a few times, then hold it at a high idle for a while until I'm able to take my foot off the accelerator without it dying. Once that point is reached (after a couple of minutes) it will drive well and hold idle well.
It acts like a car with a carburetor whose choke isn't working.
In order to try to fix the problem, I've replaced the fuel pump, cleaned & changed the idle control valve, pulled the injectors & had them professionally cleaned. The problem remains.
Is there some component that, when heated up, fails to hold the idle speed at 950 rpm or so that has failed me? As I said, it starts up and idles great when cold, but when it's been sitting 2 or 3 hours baking in its own heat, the thing just won't idle properly unless I baby it for a couple minutes first. I'm out of ideas...

[JTL]

Do you still have the original 1-wire CHT sensor? Here is a PP article on testing and upgrading it:
Pelican Technical Article: Cylinder Head Temperature Sensor - Upgrade for 84-89 Carrera

[DaveMcKenz]

Have you set the base mixture and idle speed? Are there indications of vacuum leaks?
Dave

[jlex]

Yep; I replaced the cylinder head temp sensor a few years back.... it's good.

Nope, I haven't had a tech check the O2 emissions/ idle speed. I've played with the idle speed before by jumping the IAC, then setting it to proper idle, but I've never had it into a shop to have O2 emissions checked. Does anyone really think that could be causing the problem?
I'm not thinking there's a vacuum leak involved as it runs well/strong, no backfiring, etc. & don't hear any hissing.
I initially thought it was the injectors as pressure didn't seem to hold very well after shutdown and the pressure to the line wasn't optimal, but to address the pressure question I replaced the pump (with the check valve) and had the injectors cleaned.
I appreciate the comments.