Ford RS200. It's why group b was banned. It was too fast for the drivers.
Except it was Toivonen's famous accident in a Lancia which sparked the ban. Every single Group B car of the late era was too fast - it was a formula under which Audi achieved 1000HP (they didn't race those, though).
Peugeot 205 T16 Evo 1 and 2. it didn't need a whole new design and body panels to be fast. and they used a diesel engine block if I recall right..
Audi Quattro[/thread]