well when I had a P0402 a new PDFE sensor took care of that problem, cleaned the throttle body passages also

when you replaced the DPFE did you get the newer plastic version or the older metal one? if it was a metal one it could have failed again

- 95 Mystique LS - Zetec/5spd - 99 Contour SeVT Sport - Duratec/5spd Official NE-CEG Contour/Mustang Family