A word about the PPI. Before I underwent my major maintenance at 70K miles, my mechanic gave it a once over an commented how good everything looked underneath (that didn't require taking things apart). About six months later a slew of things let go without warning. I recall a bill around that time for about $5K...again at independent shop rates, I can only imagine what that would have cost at the dealer.
Point is no matter what the PPI reveals, you must factor in known Boxster/Carrera weak spots, things that will typically go by a certain mileage that aren't part of the service schedule and simple random failures that happen to any car. Even if you're not spending ~$1,000 - $1,300 a year on these things, they are accruing just the same and will need to be done later or sooner depending on how much you decide to start driving the car.