In case you haven't already seen these, the tech articles we have on the Porsche Boxster can be helpful:
Porsche Boxster 986/987 (1997-2004) Technical Articles | Pelican Parts
Also, to maintain any older rubber parts of your car's exterior (they might be drying out as well), you might want to take a look at
Gummi Pflege Rubber Protection, which many of our other forum members have recommended.
Good luck!