1997 Mercury Marquis OBD2 codes P0174 & PO171

Could not smog car because P0174 code. Took it to a mechanic (ford doctor). He replaced the intake Manifold. ( I know the story) Gorman made in China vs Ford intake manifold. He claimed he couldn't get the "O" ring, so a kit from Ford dealer was ordered, which was Ford intake Manifold with Ford gaskets.

I took it back to smog check and it passed. Three times after around 100 or so miles. The check engine comes back on aftwer I erase it with the Equip I bought at Kragens. Now I get P0174 & P0171 to lean bank 1 & bank 2. I would like to know the proper fix before I go back to the Ford Doctor.