FRS,
Believe me it only holds that for a few seconds in a 500+ car. Cossies get to 170 quicker than you could believe with 500bhp, it is just at that point they hit an aerodynamic brick wall, and then the acceleration slows dramatically (hence I imagine, why Karl has done the boost tail off above 6000). 7k in fifth with 215/40x17s = 170mph, 6k is less than 150...