Can't get rid of p0171 and p0174 intake man

[red101]

I replaced intake manifold gasket and still get this code . checked all tubes and sensors making sure they were all on when putting it all back together. Does anyone have any idea what it could be . Thanks

 

[bill06447]

There's a whole list of things that need to be done, according to the Ford TSB from "back in the day" replace manifold gaskets, PCV valve and elbow, and the LH rocker cover with ones of the newer design. That said, did you check thoroughly for vacuum leaks from all possible sources?

Bill