Our AAN engines have electronic fuel injectors. These injectors are connected to a fuel rail that is pressurized by the fuel pump. Since there are many variables to be dealt with, e.g. RPM, load, boost pressure, etc. one way of eliminating some fuel delivery issues is to use a fuel pressure regulator to maintain a "constant" (or close to constant) differential pressure across the fuel injector. (More info regarding our fuel injectors is found here). This constant pressure differential is maintained by a fuel pressure regulator(FPR). In our case, it's a 4 Bar (58 psi) FPR (For the 3B it was 3.0 Bar and for the RS2 3.8 Bar)

The general arrangement of the fuel system and the FPR is shown here:




Here's what VAG said about the new 4.0 Bar FPR:



The fuel system PNs including the FPR are shown here:



The original UrS4 FPRs have been superceded to the 534C PN shown above. Reasons why are unclear.

This will be on the exam.