OM612 OEM Wahler EGR Valve Assembly
The EGR valve, by it's very existence and design, becomes clogged with exhaust soot and does not function properly. When this happens, your Sprinter will often blow black smoke and/or the Check Engine Light will illuminate and you may even go into "limp mode".
Excessive idling is one way to encourage premature clogging of these assemblies.
This assembly is exactly what you would get at the Dealership.