Your original pressures are super hard to me, although on 18s that actually appears to be the spec. The S didn't come stock with 18s as far as I know, so I'm guessing they are basing that spec on the non-S?

FYI if you were unaware, those numbers on the door jamb (for any US car, per regulation) are always the fully loaded numbers. The numbers for partial loads (what you probably actually want) are in your manual. Sporty cars will often have varying values depending on load - my 911 and my Audi S4 have different values, while my Ford Escape does not. I never trust the door jamb.

Here's from a 997.1 manual I found online, not sure the year, but I'd check yours since this may just apply to 997.1s.




EDIT: While I'm here, +1 vote for DSC. It's awesome. Makes the car feel so much better.