Replacing anti-run-on valve for secondary air: Notes
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 Porsche Boxster, 2003 Porsche Boxster, 2002 Porsche Boxster, 2001 Porsche Boxster, and 2000 Porsche Boxster. However, it is still accessible from the selected car via links, so may be relevant.
If the anti-run-on valve or the check valve are defective, the secondary air system must be converted to the system used as of model year 2000.