I would take off and clean/replace the egr valve. The are pretty easy to get to. Depending on how much they cost I would just replace it. I would also clean out the egr tube from the header to the valve. Another option would be to buy a block off plate and a cap for the header and a egr delete sensor plug. I think it cost me around 50.00 to delete my egr setup which in most cases is cheaper that buying a new egr valve but I would try to clean it up first if you want to keep it. It will probably end up needing replaced though. Good luck