What is a one-sentence summary of the following article?
If the valve is stuck closed, the car won't run well at higher RPMs (on the highway). It may just need to be cleaned and not need replacing. If cleaning the EGR valve does not work and you are still getting code P1406, the EGR valve needs to be replaced.

Summary:
Look for the Engine Code Error (EGE) P1406.If the EGR valve is stuck open, the car will run sluggish at lower RPMs. Try cleaning the excess carbon out of the EGR valve first.