928 110 198 02AM - Early 87 Billet Fuel Pressure Regulator - Aftermarket
This is used exclusively on the early 87 S4 cars that use a rubber Hose (928 110 359 04 - 928 110 359 09) from the Fuel Pressure Regulator to the Console on top of the Bell Housing. The 87 Fuel Pressure Regulator is #4 on the PET drawing.
You also need hose 928 110 359 09, which is not included, to complete the assembly. This hose is #10 on the PET drawing.