truck running rough, advice needed

[markNtennessee]

My 01 5.4 expulsion has been running pretty bad for a while and it never would throw a code, but I finally got a code the other day and I'm getting p171 and p174 codes. After researching the internet about the codes, it seems that the common culprit is the PVC tube, but I replaced that assembly about a month ago. I have also checked for vacuum leaks and cleaned the mad. So does anyone have any ideas what might be causing my truck to run lean

 

[ssbroly]

Mine was throwin the lean codes, and it ended up being a intake manifold gasket that was leaking on the back of the block. Problem was, when it warmed up all the way, it ran fine, just a CEL. I spent 3 weeks trying to figure it out, shop had it for 5 days before they could figure it out.