THE S6 is equipped with an electronic stability program (ESP). In addition to the levels of roadholding afforded by the quattro four-wheel drive system, ESP further improves car control by monitoring and manipulating a variety of systems. These include the functions of the anti-lock braking system (which itself is assisted by electronic brake-force distribution), electronic differential lock, anti-slip regulation, engine drag torque control and the higher-level yawing moment controller. That's a lot of electronic gizmos to digest, but basically ESP can detect, and then counteract, any oversteering or understeering tendency.