DIY guide on replacing the engine air filter in the 987 cars. This is written from a 987.1 Boxster. Cayman owners can start with page 4 (first 4 pages dedicated to putting top in service mode and getting to the engine cover.
This should also apply to 986's - for the most part. Good luck!

https://www.box.com/s/2b0a1132ac51680b0d6b