Code refers to the pintle being stuck open when the pcm has commanded it shut, make sure the passgae is not carboned up causing the pintle not to seat and the harness and connectors are ok. Then you should have a scan done with a bi-directional scanner that can command the egr to see the results, if commanded closed and it fail this command the engine would run rough and vacuum would drop off. Also see this link.
http://service.gm.com/gmspo/mode6/pd.../2001file4.pdf