2001 F-150 4.2L 4x4. I have been fighting this code for about a month. i have replaced the dpfe sensor. checked all egr ports all are clean even removed egr and cleaned ports and egr with berryman. tested egr valve with vacuum pump, results were egr opening strong to low idle but will not stall engine.tested evr, has strong supply vacuum from intake and gronuded pin 33 causing evr to open egr and stall engine. tested vacuum hose from evr to egr, clear, has no vacuum at idle and around 5 hg at 2000 rpm. cleared codes and CEL came back on at about 10 miles into the second drive cycle (cycles being 20 miles).. Dont know what to do next! seems egr system is operating correctly. anyone have any ideas? thanks for all you advice in advance.

 

Seems you did all the right testing and got the right results.
I would suspect the new DPFE is faulty or the plug up may have a problem or possibly the small hoses or a crack in the pipe/tubes.
The test sensor (DPFE) measures the pressure drop accross a restriction in the main tube.
It is correct for a second drive cycle action to get the 401 code again if the fault is still present becuse the system checks two times for failure before a code is set and the light comes on.
Be sure it's still a 401 code and not something different..