High idle issues: revisted

[Whizbang]

okay, i still have not found a good solution to my high idle problems and its driving me up a wall.

Here is what the car is doing:

Generally in the morning, ill start the car, it revs high for the 3k warm up, i tap the throttle it goes down to about 2000 rpms. During the course of driving to work, it usually tried to idle between 2000 and 2500 rpms. During lunch time i will choose to idle between normal and 2000 depending on the day. I have watched it idle at about 800 rpms fine. Then just start climbing to 2000 or higher.

What sensors, if not reading properly, can cause such idle issues? I have also noticed the car is running richer (more pops out of the exhaust) and i am thinking they are related.