That is one of the plastic sparkplug connectors, I am trying to remove to get at my sparkplugs on my 1995 C220. When I remove the metal access panel on top of the valve cover aluminum casting the upper portion of that connector is visible with the wires coming out of it. When I try pulling on that connector with a considerable amount of force, it will not pull off of the plug. I don't want to break it ($18 apiece).