[deliriousga]

It's a used car so he should have had it inspected BEFORE he bought it. If you didn't sell it to him with the option to have it inspected within so many days, it's not your problem. $5K in repairs on a Porsche at a dealer is not (relatively speaking) that big of a deal and they should expect it in the future.

I think you should tell him you're sorry you didn't know about the problems he's coming to you with, but that's just the way it goes if you don't do a PPI.