Did you ever find a solution to this as i have the same problem?
2003 104k 1.4
Startup revs to 2k then drops to 1500, then gradually drops to normal 850 when warm.
It wants to tick over at 1500rpm while driving so pulls the car along without touching the throttle.
I've cleaned the map sensor and i have tried a different throttle body as the IAC is part of this, but no different.
I was thinking maybe the throttle position sensor or MAP sensor next but i don't want to just keep changing parts as it tends to get expensive quickly.
Any advice greatly appreciated.