I was searching numbers to see how fast RS7 can reach 60 from 0 and now I see why you say the fastest 4 door. Yes it is the fastest 4 door. 0-60 in 3.2 second according to motor trend. wow....
Also I found this link explaining the Quattro and engine braking.
http://en.wikipedia.org/wiki/Quattro...-drive_system)