Re: MAF sensor measurements
Hammer it's not based on the rpm it's based on the load. If the engine is just reving under no load the voltage won't go that high. Under max load the voltage should rise above 4.5volts. A quick blip of the throttle will increase the load and hence the voltage value will jump briefly. If you can rig up the multimeter while your driving you'll see far larger voltages. 5 volts is maximum and it's unlikely that the car will ever consume this much air, even under full load.
Hope that better explains it.