Alright guys, here it is:

I have a 2001 f-150 with the v-6 engine. I am getting the p0171 and p0174 codes (system lean) and here is what I have done. I have a new MAF sensor, a new DFPE sensor, new o2 sensors, new PCV valve and lines and a new EGR. I finally took it to a mechanic and they said it was the intake gaskets. I just finished replacing the upper intake gaskets. The code came back again what is left to do. Please help.

Scott

 

Since you still have the symptoms of a vacuum leak, take it to a shop that has a smoke machine for diagnostics.

Steve

 

take and spray brake cleaner around the intake's and listen for idle change indicating vacuum leak. Also check fuel pressure while running and make sure it's in spec. Also check vacuum hoses for cracks or hoses that may have fallen off. Lean codes usually come from unmetered air getting into the combustion chamber or lack of fuel being delivered to the same place.....