Hello, still having problems with P0401 because i haven't cleaned EGR deposits out. The reason i haven't done that is because i did the test and when i sucked air from the "UFO" thing, the car wanted to stall. So does that mean that the EGR does not have to be cleaned and maybe i should start changing the DPFE sensor??

This code came on when i put on headers on my truck and took those ugly one tube manifolds it had.

Thx bunch

 

If you apply vacuum to the EGR valve and the engine stalls or almost stalls then the EGR passages and valve are working. The most common cause of a P0401 in that case would be a bad DPFE.