Have a 2006 E350 with a fuel pump assembly that is leaking at top of the unit and filling the well in which it resides with fuel. The leak is not due to a faulty seal ring.

The replacement fuel pump offered by M-B is now on its third version (PN 211 470 41 94); the dealer's parts department states that installing this new style pump also requires installation of a new style auxiliary fuel pump (211 470 40 94) that resides in the right side of the fuel tank. I see no reference to that in EPC nor are any tech bulletins posted to that effect on WIS.

Is this statement by the dealer correct? Are these paired units?