2003 Cadillac Deville Deville Running rough at idle

My car is running ok while driving, but at a stop(in drive, neutral, or park) the rpm's drop and surge and at times almost feels as if it will stall. The check engine light came on and the codes stated that both banks were running too lean.

To date I have replaced, mass air flow sensor, fuel filter, all fluids, fuel injector cleaner, and have searched for vacuum leaks finding none.

Any help would be appreciated.

Thanks