You always measure between pins on the MAF, not pin to ground. The MAF circuit uses a differential ampliflier circuit which uses the difference in voltage between the two outputs to determine what the signal is.
Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.
The figures below are approximate outputs with a stock system. Your results with aftermaket parts may be different.
At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt