Round 6 of the 1981 World Rally Championship. First year of the quattro in rallying and the cars were changing from one event to another. In an effort to bring down underhood temperatures, Audi removed the inner set of headlights and replaced them with a screen and movable flap to allow air flow to the engine compartment. Mikkola and Mouton were leading the event but were disqualified for the non-homologated air vents. This lead to homologation of the more common and well-known large 'sport' style grill.
Headlight opening vents disqualified the quattros from the rally.