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I suggest you buy:
101 Projects for Your Porsche Boxster
good book and you support pelicanparts.

Or, if you're cheap:
Porsche Boxster 986 (1997-2004) / 987 (2005-2008) Technical Articles | Pelican Parts

In particular:
Pelican Technical Article: Boxster Air Filter / Pollen Filter Replacement - 986 / 987