Ford Repair: 1997 F-150 runs rough, vacuum leaks, fuel filter

Question
I have a 1997 F-150 4.6L Triton. It runs very rough and has lost a lot of power. Gives 0171 and 0174 codes (I think -- I know it's too lean on both banks).  I have replaced the MAF, plugs & wires and fuel filter. No vacuum leaks have been found.  A mechanic told me about a TSB 1998-06-11 (can't find it anywhere) that says to replace F65Z-9600-AA (air cleaner housing including MAF), but I hesitate because I already replaced the MAF and this part is another $400+.  Any ideas?

Answer
Hello and thanks for the question...I'll try to help.
 What I would suggest is that you look at the data from the engine while it is running under load. You might be able to pick up on something that is strange and out of range but not setting a code. Also, there have been concerns with carbon on the runners of the intake.....something to think about?
Hope this helps,
Erik