I have an idling problem that I can't track down. The engine will idle at 800 rpms, but not absolutely smoothly, and will occasionaly suddenly stall out. Also, sometimes when started, it won't idle at all until it's warmed up. This is intermittant and seems to occur after the car has been run a while and is then restarted after a few minutes. It's a 93 245 with 118,000 on the engine. I'm the second owner and have had it for about 5,000 miles. It has the LH 2.4 FI and the EZ-116K ignition. Here's what I've checked/discovered so far:

1. No codes from either the ignition or FI (sockets 6 and 2).
2. Car never had the O2 sensor replaced, so I replaced it w/ Bosch OEM.
3. Spent about an hour checking for vacuum leaks using soapy water. Successively pulled off all vacuum lines I could find and verified that the idle decreased.
4. Used the Bentley proceedures to check the throttle switch, air control valve, and air mass meter. All within spec (according to Bentley).
5. Spark plugs seem to have a bone-white deposit on them (or are burning lean), but gaps are correct. This made me suspect that it was burning lean due to a vacuum leak, but can't find a leak.
6. Replaced a hard plastic vacuum line from the charcoal cannister to the throttle body that was cracked, but this port doesn't produce vacuum at idle.
7. Air cleaner OK, but the pre-heater flap and thermostat has been removed. I didn't think this was a problem, since the stalling has happened when it's been over 80F (this is Dallas, TX).
8. When I turn on the A/C, the Bentley manual says the idle speed should increase, but it doesn't.
9. Haven't checked the fuel pressure yet, because I don't have the correct adapters for my fuel pressure gauge.

Any ideas? Thanks.