It's more probable for a C4S to beat an M3 than an M3 to beat a Turbo, reason being it the similar performance between the two. All it would take is a poor shift from the M3 driver and the C4S would be there or there about.
Another problem with racing at up to speeds in access of 170mph on public roads is not everyone will be as committed or foolish as you. Where they may race you up to 130mph their willingness to continue to the max at full trust might not be there. So you may have felt that your M3 was quicker than a 997tt but the reality was that you had just been the more daring.