I have never seen an O2 be a lean bank issue. Please read this link
GearChatter.com :: View topic - DTC P0171 or P0174
That should give us a good understanding of how/why the code sets.
From my experience I have found this code to typically be:
The metal tube under the throttle body from the EGR to the LIM. These crack at the lim where the piece holds it.
Vacuum lines cracked/broken: specifially on the NA at the throttle body. Look at those silly goofy connections and ask yourself..how can they not split and leak.
UIM to LIM gasket. It's not all that common. But when the bolts go in with 89in lbs of torque (hand tight if that) and you are worried about breaking the plastic manifold (97-03), it's understandable.
TB to UIM gasket: It happens..and it's pretty common.
PCV: Missing an o-ring top (cap) or bottom (under/on pcv) is quite common and would cause this.
Battery cables: Yes..the cables being corroded not only at the battery but inside the cable itself can screw with voltage etc just enough to throw P0171 and send you on a 3-4 month journey that lands you swapping on new cables because you have no hair left. Pull the cables off the battery, remove the bolt and then pull the plastic boot off. Take a good look. Any corrosion is bad.
FalconJohn has a thread going and I took a look at his car. The only thing I could remotely find were a bad vacuum line at the TB and his battery cables were questionable. He's still fighting the code, replaced the positive cable..and I'm awaiting him to replace the negative cable... FWIW I shotgunned a good used O2 on the car and there was no change.
