Pressure regulator

Left: The fuel pressure regulator (arrow) is connected to the throttle body by a vacuum hose. It regulates system pressure by increasing or decreasing the fuel flow back to the fuel tank.
Right: The throttle valve position is reported to the control unit by the throttle valve potentiometer (3). The throttle lever (1), to which the accelerator cable is attached, is located on top of the throttle body (2).
Pressure measurements require the appropriate pressure gauge (V.A.G 1318) with a shut-off valve and adapter. At idle, the fuel supply pressure should be approximately 2.5 bar; with the vacuum hose disconnected from the pressure regulator, it should rise to 3 bar.
Test yourself
A quick Audi 80 quiz: every answer comes with an explanation and a link to the manual page.