This is on a 2001 4x4. The rubber 90 on the exhaust return to the egr system. Is this a dealer only part?

 

No but they are hard to find Auto zone or maybe pep boys would have something that will work. I had a simalier problem when the 90 for my brake booster lost its O-ring. I could find every one but the one I needed so soon enuff I ended up at one of these places. And It was not behind the counter it was just down one of the isles.

 

Chevrolet part # 10217106

 

That elbow is for the secondary air injection system, not EGR. With all that gook in the image, the check valve might be bad allowing exhaust to contact the rubber elbow causing the elbow to burn out. (The check valve has the hex fitting)