Originally Posted by Karl

You CANNOT use the lean burn 1.6cvh head on a std RS turbo bottom end. This is because the std RS turbo has a 2mm piston protrusion at TDC above the deck height. The head gasket is only 1.5mm thick, and hence if you fit the lean burn head to a std RS turbo bottom end, the pistons will make heavy contact with the combustion chamber "beak" resulting in horrendous noise and bent con-rods!!

A second issue is the high compression ratio this results in, but that is insignificant in comparison to the 1st problem!!!!!