newbie...need help w/ 99mustang codes p0304 p0174 p1401

do these have any thing in common? DPFE SENSOR HAS BEEN REPLACED...3.8L V6

Did you buy the DPFE from aftermarket or the Dealer? If aftermarket, take it back and get one from the Dealer.

Also check vacuum lines (including PCV system) for cracks, splits etc.

Check/clean MAF.

Check EGR ports and ensure they are not plugged.

THANKS for the replies!!! still workin on it...a little history...had a p0401,couldn't pass inspection ..checked egr valve-ok..cleaned some carbon deposits[what i could get to] drove 140m+ to clear code [after pulling neg cable] and THEN "service engine soon" light came back on...took it back apart, checked & cleaned egr parts NOW,IT IDLES ROUGH WHEN IN GEAR .. went to auto zone had codes pulled NOW p0401 is gone but, i now have p0304,p0174,p1401...AFTER THAT,i changed out the dpfe sensor..checked& still have the same 3 codes ..seems like it may be something i did while working on it...checked vacuum lines..replaced 2 segments,re-checked my work/connections..looked at maf sensor..LOOKS ok..cleaned pcv..cleared codes & drove 40m ...light hasnt come back on yet but still idles rough in gear...i just KNOW that somebody who knows their stuff could take this info and help diagnose the problem.. 99 mustang 3.8l v6..PLEASE HELP..DONT WANNA GIVE UP AND CANT AFFORD A MECHANIC

FINALLY!!!....CLEANED EGR VALVE AND TUBES AND PORTS ONE MORE TIME..CLEARED CODES.. IDLES AND RUNS GOOD NOW GOT INSPECTION STICKER ..MANY THANKS FOR ALL THE INPUT

Congrats...glad you got it fixed.