Our AAN engines are controlled by a computer (ECU or "ECM"). This ECU uses a manifold absolute pressure (MAP) sensor in the ECU to determine what the boost pressures are. In order to compensate for higher elevations and lower atmospheric pressures, the ECU also receives a signal from the F96 altitude/barometric pressure sensor via a grey wire with a black stripe going to Pin T9/55 on the ECU connector as shown in this ECU Device List and pin-out

Here is what VAG says about the F96:




The 853919562 (Bosch 0280101001) F96 Altitude Sensor is very common across the Audi turbo line as far back as the 1985 Turbo 100s, through the 200 20vt S2, UrS4, UrS6, the RS2 and, more recently, the cars with the 1.8t (to about 2001, including the A3s and A4s). A portion of this cross-over listing is shown here:

This will be on the exam.