Just like the 335i, the new 2010 Audi S4 is underrated.
"Audi tuner APR stuck a 2010 Audi S4 on an AWD-dyno and discovered the following. Instead of the 333 hp and 325 torques Audi is claiming, they pulled 331 hp and 336 pound-feet of torque... at the wheels! Figuring that AWD cars have about a 20% parasitic drivetrain power loss, the actual crank output of the S4 is huge. How huge? By our calculations just about 400 horsepower/torques."
Link:
http://www.autoblog.com/2009/10/28/r...is-underrated/