That's good news, I think you verified that you don't have a vacuum leak at the manifolds, or heads!!

The next thing that will throw lean codes (on both banks) is a dirty MAF sensor. Are you running a K&N air filter by any chance? They are known to contaminate MAF sensors, and IAC valves with the dirt and oil that they pass.
Try cleaning your MAF sensor (be very careful), and reset your PCM by disconnecting the negative battery cable, and touch it to the positive cable.

Good luck!!