D-jet is basically a fixed trigger technology with changes essentially based on manifold vacuum. It does not know the throttle plate position angle at all nor the exact mixture (no O2 sensor data) at any time.
The throttle switch tells the ECU when the throttle is closed,when the throttle is wide open and when the throttle is moving towards the open position.The switch consist of twenty-two contacts,with a set of wiping contacts that move across them as the throttle progresses from the closed position to the wide open position.
One wiping contact is used to inform the ECU that the throttle is closed.Another makes contact only when the throttle is wide open and a third makes and breaks contact twenty times as the throttle opens.The electrical pulses created by the making and breaking of the contacts signal the ECU to open the injectors more frequently,thereby enriching the mixture for acceleration.
The L Jetronic/Motronic throttle switch used on BMW E28s ,E30s etc...,is like what you described above,and uses a potentiometer located in the airflow meter to signal the ECU of the changes in airflow.
It cannot be fine tuned as it knows nothing about driving style, it cant tell why the vacuum level is where it is or why. The worst part is not knowing anything about ignition,
That's the trigger points function which provides the synchronizing signal for opening the injectors.
A very easy mod is to remove the plastic cover on the pressure sensor and turn the adjustment screw that adjust the air-fuel ratio if enrichment is needed after airflow has been increased.
I'm not trying to build a 10 second car for the record,I just want to improve the performance while traveling through our mountains here

I go from sea level to high altitude in no time

