Both 3800 Series II NA and SC must have the black o-ring on the PCV valve. Without it you may get a P0401 DTC error code which means the EGR is failing flow test. See link below:
http://macgp.clubgp.com/howto/pcv/pcv.html
The EGR valve is located on the right hand side of the supercharger and throttle body. The black cylinder looking object with the electrical connector. It can be removed and the spring loaded pintle and other areas can be cleaned with carb cleaner. It may have lots of carbon. Make sure pintle moves freely. Then spray with WD40 before re-installing.
The o-ring is a common item and available at places like AZ. Good luck!