Auto vs Manual? You probably have 2.73s final drive as an automatic unless it was optioned to be equipped with 3.23s. The same goes for the other A4 car you raced, he is also most likely 2.73s which is why you beat him. The problem is the M6 car that has 3.42s as his final drive. That steeper gear will always out accelerate a 2.73 car unless you're making gobs of extra power or running up to high MPH. Do you know what your final ratio is? If not it's most likely the final drive that is killing you.