2000 F150 EGR Problem?

I have a 2000 F150, 5.4, 50K miles and it would not idle at start up. I did not have any lights come on and it ran fine before the problem began. I checked the intake "butterfly" and found that it was clean in front of it and carboned and sticky from the back side. I cleaned it some to unstick it without removing it and the truck began to start fine but it soon stuck again. I know now that I need to remove it and give it a good cleaning. Is there a way I can tell if I have a bad EGR valve or if it's a sensor causing the carboning problem or should I just replace both? Any suggestions are greatly appreciated. Is this a common problem at 50K and would the EGR be replaced at any specific mileage as a normal maintenance item anyway?