Whilst doing the coolant temp gauge sender buried at the back of the head had to remove a big round plastic thing that tha was attached to the rocker cover (part of the egr system i think) now that was full of hard oily crud as was the metal pipe that runs along the side of the rocker cover and goes into a hose attached to the air cleaner box and turbo. Well worth cleaning these out i reckon as mine was full of kaka at only 78k miles