I went thru the same thing just a few months ago, same symptoms, same cleaning, same research, same troubleshooting...
The garage is going to put a scanner on your car, See the MAF code and throw a new MAF on it. Why not save the diagnostic fee and their markup and put a new MAF on it? Persoanlly I would try another junkyard pull off a lower mileage car.
Another thing to consider is that the low voltage code can also mean that air is getting in unmetered (ie - not thru the TB) which is why I suggested checking for an intake/vacuum leak. That code basically means the computer is seeing that the maf reading is much too low for the rpm'* the engine is turning.
98 SSEi 111,222 miles.
Intense PCM, LS6 Valve springs, PEMS, FWI. Hawk Street Pads.