Replacing anti-run-on valve for secondary air: Notes
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2005 Porsche 911, 2004 Porsche 911, 2003 Porsche 911, 2002 Porsche 911, and 2001 Porsche 911. 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. A list of new or omitted parts is attached to the aforementioned Technical Information document.