As a suspension or steering failure was suspected, the BMW team with Quester and Hubert Hahne withdrew from the race, as did Mitter's teammate at Porsche, Hans Herrmann.

He out-qualified his three team mates at Surtees and finished 9th ahead of Hans-Joachim Stuck and double World Champion Graham Hill in the race, but scored no championship points.

Quester then focused again on European Touring Car Championship to drive a BMW 3.0 CSL for Schnitzer Motorsport.

On 15 January 2006 he won the 24 Hours race at the Dubai Autodrome on a BMW M3 together with Hans-Joachim Stuck, Philipp Peter and Toto Wolff.

Stuck and Quester returned in the 24 Hours Nürburgring, but their BMW was destroyed in a crash at night that involved an oil spill and seven cars.