I have just removed the cylinder head from my 100 2.0E. It was running on two cylinders, with low compression on pots 1 & 2. The reason was a quite large groove in the cylinder head between 1 & 2 (about 2mm deep by 10mm wide). This looks to have been worn, perhaps burnt, into the land between the two combustion chambers. Has anyone seen this before, or does anyone have any idea what might have caused the phenomenon?