hwade, not all problems are caused by the air flow meter. When the diagnostics come back with an O2 error, that's usually a good place to start. Although, a good MAF cleaning isn't a bad idea every now and then especially if the air filters haven't been changed in a while.
To test, jack up the car, usually when the engine is warm, unplug an O2 sensor, turn the car on. If the problem gets worse, turn the car off, plug that O2 sensor back in, unplug the other O2 sensor, turn the car on and if the problem doesn't change, then you know which sensor is Bank 2.
If I'm not mistaken, bank 1 is on the right hand side. At least, on my V12 cyls 1-6 are on the right, as spark plugs 11 and 12 have been refered to being on the left.
Also, do you notice if your exhaust smells 'normal'? An indication of a knackered O2 sensor is usually a 'foul' exhaust smell, it makes your eye's burn and you gag and gasp for air more easier than 'normal' exhaust. There is also an error code of 'mixture too rich' if an O2 is bad.
(NOTE: This thread was posted over a year ago!)