Presuming it operates well, this is likely a vibration problem at the pump/filter/accumulator mounting bracket. Make sure everything is tight, and the rubber isolators the assembly hangs on are in good shape. If the mounting bracket is bent, or the new components are not the exact same diameter as the old ones such that bracket no longer clamps tight on them, you can wedge in bits of rubber hose (or similar) to take up the slack. I had this exact problem with my single pump setup.
1986 300E 5-Speed 240k mi.