It is covered in crud, has gouges in the bodywork and in some places the paintwork is badly chipped. Porsche usually like to present its luxury cars in glistening showroom condition, but this particular 911 wears its layer of dirt with pride and it will not be going through a car wash soon. After all, the grime doesn’t come from just any old place, but from the summit of the western ridge of the Ojos Del Salado. As the highest active volcano in the world, the peak lies on the edge of the Chilean Atacama Desert and has the same appeal for extreme car drivers as Mount Everest does for mountainee…