01 mustang egr insufficient flow

Okay, all you Mustang aficionados, I’m new to this forum and I have been battling the same problem for a while. The car has 43K miles on it and the engine is a 3.8L. The emission code it keeps throwing is the dreaded P401, EGR insufficient flow. I’ve removed the plenum checking for restrictions in there. The intake was clear. I tried cleaning the Differential Pressure Feedback Electric (DPFE) switch with no luck. The light stayed off for a while at highway speed but came back on at in town driving speed. I replaced the DPFE switch and haven’t had the light yet, but I haven’t driven the car much. I have to drive to ST Louis today. If it does come on again, is there some simple check to drill-down to the root of the cause?:banghead:

did you ever cure the 401 code,hi, Steve here in middle of Mo.my ford ,when first starting it will surges at idle,engine light is on and throws a 401 code,(excess air flow),I've replaced ever thing in the EGR system! and no luck,when its cold the car sometimes dies after idling for a few min's, you mentioned that replacing ,(or was it reprogramming)the computer may fix the problem in one of your replies to another member on this site,I was wondering if you had any work on your computer that may have cured the problem in question?or can the stock computer be recalabrated too, or beyond the normal realms to compensate ? or can I install another brain box (say a MDS, or Jacobs,or maybe a chip) inline in the same system?give a reply if you got the time or know someone that might2001 3.9 332