Good list, Ed.. see if my thinking is logical for each one:
MAF sensor - This is what I'm leaning towards, I think it makes the most sense by process of elimination.
vacuum leak - Would this be intermittent?
low efficiency cat - The code says "range 1", which I'm assuming is talking about the oxygen sensors before the cats, so I wouldn't think that would affect it..
low efficiency oxygen sensor - Shouldn't be. All 4 sensors are less than 7k old, and this CEL shows up for both banks, it would only come up with cylinders 1-3 or 4-6 if it were one failing sensor, not both sides I would think
problems with wiring to sensors - Again, I think it would only throw a code for one side, not both.
I dont like those stinken CEL lights - I hate these buggers, too! I think everyone does
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