It's usually a good idea to do multiple test drives of a particular model before you buy it. That way you'll get a feel for what's normal or not. It's a used performance car, chances of you test driving a dud the first time isn't that unlikely.
I test drove the hell out of M3's before I settled on mine. The difference between a neglected and well treated one is pretty significant. The driving experience can be night and day between the two.