Originally Posted by Thor80

You may want to look/post in the Modular V8 section found here:
Modular V8 (4.6L, 5.4L) - Ford Truck Enthusiasts Forums

I had a lean bank 1 code on my 99 Expedition ended up being the PCV hoses were rotting away. But it sounds like you've checked that already. Anyway you may have some luck in the V8 forum as this is more of a motor specific issue.

-Torsten