I noticed something similar on my 2002 Aero. I brought it in last week for some other things and had them take a look at that too. It wasn't bad to begin with, but it was noticeable. When I mentioned it to the tech he told me that was an easy fix like he had done it many times before. They ended up adjusting the "base idle" - that's what it says on the bill. It still does it, though not as bad.