On my E320 the block just slides down onto the plug and those "screws" do not really hold anything down. The block has a hole that fits down over/around these so-called screws. You should be able to just pull the block straight up/out. Post a pic if you can. I think you are seeing an attanchment there that ain't really holding anything. I have always assumed the "screws" to just be some kind of guide pin.