The VAM in a Vane Airflow Meter. It is used on some fuel injected cars, mostly older ones and is not original on any stock, carburetor Pinto. Thus, the Pinto never came with a VAM. The VAM is generally mounted between the air filter and the throttle body to measure air flow. It has a spring loaded swinging arm that is moved by the draw on the engine. Basically the more the throttle body plate opens, the harder the draw and the more the vane in the VAM moves. The vane itself is connected to a potentiometer. Thus, as the engine draws, and the vane moves, the change is registered in voltage that the computer uses to determine the amount of fuel that gets injected.
The most common application of a VAM is on a Turbo Motor swap into a Pinto where the factory set up is used. That said, for those who use a normally aspirated injected engine (again factory) the VAM is also applicable. The MAF has replaced the VAM on newer cars. There are others who choose to not use the factory setup and use the more modern MAF with an aftermarket system. A small VAM was used in a non-intercooled Turbo Coupe (83-86). The large VAM is used in the intercooled Turbo Coupes and requires the associated injectors and ECU (computer). There may be other variations on the normally aspirated 2.3's and the SVO engines (I just don't know).
The Pinto is rather limited for VAM room as it is about the size of a smaller shoe box. By contrast a MAF is a small piece that inserts into the air intake tube. Because of the area limitation for mounting a VAM it winds up in odd locations in a Pinto. In my case I actually put it (and the air filter) in the passenger front wheel well. I'll include a few pictures to help. The first is the VAM itself. The second installed in the wheel well of my Pinto. The third is the convoluted mount I had to fabricate to support the VAM. What is not seen in the second picture is the notching of the lower headlight shield for clearance and also in the bumper bracket so as not to restrict airflow. Even the alternatives are tight.
If you have aspirations for the turbo swap be aware that the parts aren't falling off trees anymore. In 2008 when I started my swap (and I had a donor '88 TC to begin with) I still needed many things. There were about five TC's every time I went to Pick your Part. Then..., within about six months they dried up to the point where I have seen one - in three years. And I went every month, to two different yards in the large market Los Angeles area. The best thing to do is to buy a donor car, but the early cars have the better bellhousing setup while the later cars (87-88) have the better motors by about 25 HP.