If the seller is coming off as particular as to who they sell the car (because they want it to go to a good home) but is reluctant about handing it over for a PPI, I'd suggest to them that you both could go to the dealer, check out some Porsches and maybe grab a meal while waiting...who knows, a little bonding *might* work in your favor when it comes to price.
Again, I'm not advocating purchasing this particular car, but if it's really speaking to you, I think it's worth the second look (and PPI). In a worst case scenario (ok, scratch that...I can imagine much worse) you end up doing all the things you mentioned and spend $6000...you still get a heck of a lot of fun for $15000. BTW, we are all going to take a bath on resale (with maybe the exception of 78F350, lol) so end the end, it's only money, right?
