If you had a scan tool, you could view the idle rpm request, and see where the computer wants your car idling at.

I believe the computer is supposed to run in Open Loop status for the first 10-30 seconds and run a rich condition until the O2 sensor can start sending data to the PCM. It will request a higher idle until the O2 sensor starts feeding info, and computer goes into Closed Loop status, and take over fuel monitoring and timing etc.