In 2004 he also drove races in the European Touring Car Championship for RS-Line Ford, the brand he runs a dealership for at Ammerbuch.

From 1999 until 2005 Asch raced the 24 Hours Nürburgring, aboard the Nissan Skyline GT-R entry of Japanese team Falken every year as their lead driver.

He last appeared on the race in 2010, in a project made by German magazine Sport auto (Germany) and Porsche test driver Walter Röhrl, who did not take part for health reasons.

At the end of the 1999 and final STW season at the Nürburgring, Asch was again accused by some of hitting an opponent intentionally to support his Opel teammate Uwe Alzen.

Alzen celebrated immediately after the race, but the championship was given to Abt in November after Asch's move on him in the last corner was considered deliberate action by a DMSB court of appeal, based on video evidence.