Yes, as Shertex says this subject has been discussed and discussed. The US E320 CDI is equipped with a Beru system that uses 5V plugs.
Mercedes service/repair documentation is very clear on this, that is why I said to use Beru 5V plugs only!

What's best for a W123 240D or W126 300SDL, is not always best for a W211 E320 CDI. If you're not using MB genuine parts,
you need to make sure you're buying the correct OEM part(s) for your car.