Remove the intake manifold and electrical connectors, laying the harness aside. Discard the aluminum fastener and wrap a clean shop towel around the fuel line nut to loosen it. Seal the fuel lines with special tools 13 5 281 and 13 5 282. For N55 engines, move the additional harness over the fuel supply line fasteners out of the way to access the fuel supply line. Loosen the fuel line nut in the specified order, then remove the fuel line bracket fastener and the fuel line, sealing the connections with matching plugs from tool kit 32 1 270. For N55 engines, remove the electrical connector and the oil temperature sensor. Next, remove the high-pressure fuel pump mounting fasteners and the pump itself, being prepared to catch any dripping oil with a shop cloth. When installing the high-pressure fuel pump for N54 and N55 engines, ensure the fuel supply line has the correct elastomer mounting clamp, replacing it if it has a welded hold-down clamp. Dispose of any copper sealing rings if present, as they are no longer needed. Replace the high-pressure fuel pump O-ring and clean the mounting surfaces before installing the pump, rotating it until flush with the mounting surface. Install the pump fasteners finger tight and lightly coat the fuel line connections with transmission fluid before installing and tightening both fuel lines finger tight. Listen for an audible click when connecting the fuel supply line quick-connect fitting to ensure it is locked into place. Once all lines and fittings are positioned and stress-free, tighten the fuel pump fasteners and the fuel lines in the specified sequence to the proper torque. For N55 engines, reinstall the oil temperature sensor and reassemble the engine. Finally, check the fuel system for leaks and verify fault codes, resetting the ECM memory as needed.