It has been argued on the s4 board, and mentioned here, that the S4 has an advantage against the M3 at altitude. I understand what turbos, superchargers and blowers are for. I know cars at altitude suffer from less oxygen density but how can a turbo, which relies on pulling in more air for it's normal hp, provide any more performance against a na M3 which is using the same air? It is my opinion that there is no change in the relative performance between the 2 cars at altitude...(The same 2 cars at sea level will perform better, with the M3 winning of course)