Over last few weeks have had a 401 code on computer: EGR flow insufficient. This is on a '99 F-250, 5.4 engine with 60k miles. I have used the Actron code reader and cleared the code on several occasions. Each time, the "check engine light" will remain off for a day or so and then come back on. Today, I removed the EGR valve which looks fairly clean, but had a thin film of carbon buildup. I also removed the EGR valve control solenoid (EVR). It appears to have failed the test as described in the Chilton's manual. That is, once off of the truck, I could blow air through one port which came out the other. Apparently, the solenoid is supposed to remain closed unless activated(?). Could this be the source of my problem? It seems like if this were to remain open, then there should not be a restricted flow - or could it be the solenoid is stuck in a half-oen/closed position that might be restricting flow? Anyone have a similar problem? This one is making me crazy! Also, there is considerable "greasy' layer inside the throttle body behind the throttle plate. I'm hearing this is normal and to not mess with it - anyone know about that?