Need some help troubleshooting my EGR system. First, I have a 1998 Expedition with the 5.4L and 163,000 miles. I recently had the P0401 code show up on my OBD II. I immediately went to this forum where I read all about this issue. Borrowed my friends hand vacuum pump and checked out the EGR valve. When I applied vacuum to the EGR, the engine died and the vacuum held rock solid. EGR valve problem eliminated. Next I replaced the DPFE Sensor and two hoses. After a few miles, P0401 came back. All hoses are good and all connectors are solidly connected. I am unsure of my next step. Seems like many folks remove and clean the Throttle Body next. What is your opinion. Appreciate your help and response.