Apply logic here: The MAF measures incoming air and the then PCM pulses the fuel injectors to dispense the right amount of fuel. If the O2 sensor says the mixture is always too lean, that means too little fuel or too much air. If too much air, then either the MAF is sending the wrong reading, or air is getting in somewhere after the MAF.
The lean code is also the symptom, fix the rough idle and the code will go away. Since the O2 sensor was already changed it's likely not that.
1. Get some MAF cleaner from the auto parts store and clean the MAF. DO NOT use any other chemical to clean the MAF.
2. Replace the air filter.
3. Check all vacuum lines for leaks, the V-10 has the known issue Grit Dog mentioned, the hove from the PCV melting.
4. Check for air leaks, be sure all bolts are tight to throttle body and intake manifold.
5. Check air intake tube after the MAF for cracks, etc.
A lean condition can also be caused by too little fuel, so it's possible one or more injectors on bank 1 are clogged or defective, but this is much less likely at this mileage that an air leak.
