I wrote a really long post about how Audi spent a whole decade showing up at your local national touring car series with a car built just for it, with the Quattro all wheel drive system, won a championship and then went somewhere else after it got banned. The point was generally that this was the last time "road relevant technology" was a valid claim in motorsport, and almost certainly the last time it ever will be.
But really that's the whole post right there, so this one is a hell of a lot shorter.