compression ratio which makes more power out of 3 litres than a lower compression engine of the same displacement (i.e. the TT engine). The TT engine at 0psi only makes about 165 horsepower at the crank and you can't get it over about 90mph at 0psi. However, an NA at 0psi manifold pressure can get up to 140MPH easily.
*this comparison is assuming the TT has stock turbos.*