Low idle

Classic symptoms of a vacuum leak. Probably needs intake manifold gaskets. The manifold cools down overnight and pulls away slightly, You start the engine and it draws in excess air giving you a high idle and rough. As it warms up the parts expand and start to seal back up and the engine runs better because it is now under computer control. These are common for leaks between the upper and lower intake manifold sections. The pictures show the o-rings and lower gaskets that fail. Normally I test both the upper and lower gaskets, It is not that much more work to do the lowers as you have the engine apart anyway.

What are they when you start it vs once it warms up? Do you have access to a scan tool? I'm wondering if the ECT sensor is acting up as well. Does it start hard as well as idle wrong?

OK so on cold start it revs to 1K, that's common as the engine tries to warm up quick. Then it should drop back to around 650 or so and stay there. Try cleaning the throttle body and the idle air control ports, Then test the IAC for operation. Normally they fail and stick in one spot but it's possible it's sending bad data.

OK so you cleaned the TB, IAC is good and no vacuum leaks. But it still acts up.
At this point you really need a scan tool with live data to see what the timing and fuel trims are doing. The engine coolant temperature sender on these likes to cause problems but without a scan tool you can't see if it is the problem.

What does the coolant temperature sender show on a cold engine and once it warms up?

Please let us know what happens.

Cheers, Ken