F-350 random power loss, sputtering, etc
 

iI have a 2004 f-350. Sometimes when I'm driving my power will fade in and out. The truck will also sputter and sometimes bellows black smoke. The weird thing is it will go back to normal after a few minutes.

I read that it might be the EGR valve, but I'm not sure. I want to have some sort of idea what it is before I take it to the dealership. Anyone have any idea?