Hi Bellehayes,
In regards to your idle issue, if the rough idle only happens when the A/C is switch on, it is possible that you could have an issue with the A/C compressor itself. The compressor internals or electromagnetic clutch pully could be binding up a bit and causing extra load on the engine.
This article here about recharging AC on the Boxster also outlines checking the system over:
https://www.pelicanparts.com/techarticles/Boxster_Tech/97-MISC-AC/97-MISC-AC.htm
Good luck!
-Matt