I'm losing my mind and draining my wallet. Help!

[bucksandbirds]

00 EB with 4.0 SOHC 166k miles.

For the last few months, I have been chasing down a CEL.

After replacing (plugs, wires, coilpack, MAF, Fuel Filter and I cannot remember what else)
I am STILL getting a CEL for P171/174 Banks 1 and 2 Lean.

My mechanic tells me that the 02 sensors are good and that he has never seen one need an 02 sensor that is showing both banks lean.

He tells me that I need to go to the dealer for an updated program scanned onto the ECU? I have never heard of such a thing in regards to a CEL continually popping up.


What can I do here?

I have two concerns as I have no other things I can think of where the problem could be...

1. Was the coilpack that I replaced on the vehicle not the correct model?
It was purchased from O'Reillys and I wonder if they gave me the incorrect part... Is it possible for the truck to run on a different coilpack and is it possible for that to be related?

2. If it's not the 02 sensors, then what is wrong???!!???

I have THOUSANDS into the maintenance items on this truck, but I cannot keep spending $150+ a week for gas at 13mpg.

Please help. I am out of money and out of patience.

 

[snoranger]

Check for a vacuum leak.

Common causes:
Intake gaskets
Broken or disconnected vacuum hose (including the hidden PCV)

 

[windsors03cobra]

Intake manifolds gaskets I would guess, real common issue on those engines.
Yours lean on both banks your sucking air somewhere downstream of the MAF and that is why both banks are lean, pcv elbows turning too go and leaking massive amounts of air is common on all later model Fords and you can usually hear those hissing half whistle like.