Measures the absolute pressure, which in turn allows you to mitigate the negatives of a AFM.
Eg, reverbaration, dirty afm affecting the signal, removes pretty much any limit on max airflow.
Atmos based blow off valve will not stall an engine Comming off throttle will be alot "Smoother"
A pressure line will run to a sensor ( think of it like a boost sensor ).
This sensor will either be external, or internal to the ECU. Most plug in ECU's use internal map sensors, and would be what you want. You then remove the need for a AFM, and take them completely out of your engine bay.
And run a single boost line to the map sensor