Manifold Air Pressure sensors....what is their purpose....as in why is the manifold air pressure important and what does the ECU (Engine Control Unit) do with the data it receives?
It depends on the application. They can be used with and without a MAF (Mass Air Flow Sensor).
Without a MAF it's used alongside the engine RPM and throttle opening to determine the airflow into the engine, usually in petrol engines.
They are sometimes used with MAFs as well, especially on turbo engines where they are a measure of boost pressure, at least in diesels with no throttle.
They can also be used as a cross check to see if other signals are sensible.
