Sorry - I did not use the right name - it's the idle contact of the throttle valve switch. In the manual diagram it would be S29/2. However, the TSB only refers to the 1986 model.
Anyhow, since mine is not rough right now when I am at a red light, I'll wait a bit before I tackle this. Who knows - maybe it'll settle down.
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)