X2 on the EGR valve..VERY costly to replace. I was throwing a code for Mine about three years back and since it's very easy to locate and remove, I removed it, cleaned the pintle with carb cleaner and used a wire brush, toothbrush or pipe cleaner to clean off the carbon from the metal exhaust gas return tube. Installed and have never had the code come up again so far, and it's the original EGR on my 97 3800.