Fritz, you are right on the liquid cooling. I got so far into the M96 problems that I bypassed it from thinking of the 993 series too much. My error.

That aside, The method of manufacture and materials used in the TT,GT2 and Gt3 engines are not the same as in a M96 engine at all, and the M96 engine has substantially cheaper components and assembly process than a 993 or earlier series Porsche flat 6 engine.