My Cayman has an annoying rattle that also seems to be coming from behind the passenger seat. I tightened the two bolts holding the privacy cover but that did not seem to address the issue. If there are some additional things to try, I would like to do so before taking the car to the dealer. The car does not have PSE.
Is it the seat belt? If you don't have the little plastic tab pushed up it will rattle about.