Rough idle at start up

The computer controls the timing based on crank and cam sensors. Have you checked for simple things like vacuum leaks? Has the check engine light come on with any codes?

Lee:
Have you ever checked compression in that cylinder? When steel heats, it expands. I wonder if you have a low compression problem only when cold. I know that is a stretch, but the only other thing is the PCM. If you have replaced plugs, injector, fuel pressure is good, and the injector is working properly, it has to be one or the other. One last thought, have you checked the temp sensor?

I call that preventive maintenance. You did the right thing to clean the maf sensor because it is one of the sensor is most likely to cause that problem.
Beside that you have the IAC sensor and wiring.
The IAC is a kind of small nose for the engine to breath when the gas pedal is not pushed down, same as saying when coming to a stop. If that is malfunctioning, the car will feel like choking when idling.
In real life, we said"everybody is inocent until proven guilty" :-)
there is no code(s) right now, the car is driving fine so far.
Let me know as soon as possible there is other symptoms or engine light, so we can take care of it.

Without being there this is a tough one. The PCM adjust ignition timing. If everything is working properly, that is my guess.

It is attached to the throttle body

and look like this ,here seen in different positions

When suspecting a IAC problems ,first perform a visual inspection.most problem can be found in wiring harnesses, conectors(oily or corroded connectors).
an unstable idle or stalling can be cause by vacuum leak or faulty PCV valve.in some cases just dirty electrical connections at the IAC can cause a problem.
***The IAC Valve Assembly is NOT ADJUSTABLE and CANNOT BE CLEANED
If physical evidence of contamination exists, install a new IAC valve.
Testing:
Key symptom is elevated idle speed while noise is occurring.
"Snapping" the throttle can induce the noise.
While the noise is occurring, place an EngineEAR probe near the IAC valve , If the IAC valve is making the noise, install a new IAC
removal:

if the vehicle still stall after testing or replacing the IAC, nest move will be to test the computer ground.
let me know .

Yes, the knock sensor os designed to adjust the ignition timing to its most efficient point. If it is bad, it could cause the timing to be adjusted incorrectly.

Start at the beginning and find the codes in the pcm and we can go from there.

First thing to do is check yoru fuel pressure and scan for codes, start there. Then take your maf cleaner and clean teh throttle plate on both sides as they get gunked up with oil and cause similar problems. Then check for any vacuum hoses off or any hoses/valve cover connectors that are rubber for holes. Also there is tube that runs from the intake to the egr connectins that tends to get loose, you can either get anew part or try putting a zip tie on it and tightening itup, it wil last for a little while.