sIXTO, you have to turn on your DMM dialiing to Hz- %, but push the bottom "select" to change from Hz. to % or DUTY CICLE, Then you can read % in the pin 3. The right reading has to be close to 50%. If the O2 sensor is ok, and the ECU is sending electrical signal you can adjust to 50% rotating little bit the 3 mm allen on the Mass air flow Sensor.
Refering to the vaccum values, somebody in this forum said that the right vaccum values are 20 inch water column, and you report 20 inch Hg. column, which is completely different because the Hg. density is 13.6 grams per cubic centimeter and for the water is only 1 gram per cubic centimeter.