Hi....welcome to the Club
It is normal for the revs to rise to a certain level after start up and drop within a short time once the Lambda sensor goes closed loop.
However, it should only really rise to approx 1200rpm maximum.
You can calibration settings for the throttle housing via a scan tool quite easily and this should return it to normal rpm
Also, worth checking for any vacuum leaks in and around the intake system....split hoses, etc