All US market E320 (OM648) CDI's are equipped with Beru's ISS (Instant Start System) which require 5V Beru glow plugs. Only European models came with the 11.5V Bosch system.

The Bosch plugs are not acceptable substitutions or replacements for the Beru plugs, I'm not sure why so many retailers list them. Never assume, always verify with the MB EPC/OEM catalogs before ordering parts. Another example, many parts catalogs will be happy to sell you an INA belt tensioner that fits, but was never used on the W211/OM648 (W210 part since superseded by MB. Litens is the correct OEM). If you're not using OE MB parts, you really have to watch what you (or your independent) is ordering and installing on your car!