Hey Guys

I have just purchased myself a MY04 WRX. Now at cold start, does this sound normal?
Starting the car, she initially Revs up to 2000RPM but backs off to 1600, while idling at this RPM the car feels as though she is bouncing. I popped the bonnet to have a listen to the engine and it's not making any knocking noises. While driving yesterday morning in the car it felt as though the car was bouncing aswell.
Has anyone had this happen to there WRX before? Is this normal or do I need to have her sussed out by Subaru.

Cheers