Since your getting both banks to have faults in them its eather your MAF like you said, possible PCV intake leak, your intake boot is off the throttel body causing unmetered air leak, or you have a air leak somewhere past the MAF.
MAF's do tend to go on v8's, but so do PCV valves.
With the engine running spray down the back of the intake with brake clean. If the idle increase then you have a PCV leak. If it doesnt incease, spray down the front intake boot and around your MAF.
If that still doesnt do anything you might want to get the codes read out by a dealer and get a defenate on what the problem is.