This is one of the cars that made me re-think what makes a good road race package based on passenger cars. The conventional thinking in the U.S. at time was that a properly set up rear-driver was the way to go and nobody challenged that assertion until Audi campaigned a pair of AWD (Audi Quattro system) cars in SCCA's Trans Am series and IMSA's GT Championship in the GTO (over 3 liters displacement or smaller turbocharged engines) in 1988 and 1989.

I saw the Audi GTO cars in competition at Laguna Seca being driven by the legendary Hans Stuck and Hurley Haywood. You could hear the wastegate 'chirp' between shifts even before the car came into view.

This YouTube vid is audio, only - no video footage to accompany the engine sounds. Most of the audio is from in-car recordings, though some are from trackside:

http://www.youtube.com/watch?v=UsMQRRVPmDw

Link below is a vid shot in 2005 when both the Trans Am and IMSA GTO cars were brought out of retirement near Audi headquarters in Ingolstadt, Germany for an exhibition. Amazing, the cars were kept in running condition after all this time. You'll have to excuse the 'shaky' cam, but the sound is worth it:

http://www.youtube.com/watch?v=6KI_q76QBUg

IMSA GTO car pics.

TransAm car pics. Notice the carbon fiber driveshaft and rear differential-driven alternator, the latter relocated for better weight distribution.

In both racing series, the cars utilized Audi's passenger-based 20-valve inline 5-cylinder engines, turbocharged for output up to 700 crank horsepower.