I had an issue with the EGR valve on a Chevy 3.4l once.
I just took it apart and saw that it was full of carbon deposits.
I scraped it away as best I could, blew 130PSI air into it and put 'er back together.
Never had an issue with it again.
I
have, however, seen them all melted and disfigured, caused by a clogged catalytic converter - but that was a Chrysler - yech.