In the early '80s, the FIA devised a new set of rules for production based race cars that could be used for both track racing and rallying. The Group B rules spawned some of the wildest homologation specials devised at that time. Under the rules, a minimum of 200 production models had to be built (not necessarilly sold) and then evolution specials could be derived from those. Some of the products of Group B were the MG Metro 6R4, Ford RS200, Peugeot 205 Ti16, Ferrari 288 GTO and the Porsche 959.
Only a couple of GTO Evoluzione models were built and they eventually spawned the legendary F40. Most of the Group B cars ended up competing in rallies around the world and were the ancestors of the later World Rally Cars like the Subaru WRX and Mitsubishi Evo. Many of the production models remained unsold for years and ended up going at fire sale prices, especially after a spate of rally accidents with the high powered Group B cars that prompted the FIA to cancel the whole category.
There's more after the jump including two incredible videos of the 959 in action.
The GTO never did race in it's original form, but it's arch-rival, the Porsche 959, did actually have some competition success in rally form, most notably at the Paris Dakar Rally. In 1986, running with unusually long wheel travel for a 911 derivative, a pair of 959s ran the distance from Paris across the Sahara to Dakar faster than anyone else and finished one-two. None of the Group B cars were ever US legal, although some individual examples did make the crossing, including a pair of 959s bought by a couple of guys from the Seattle area named Bill and Paul. If memory serves they were involved in some business related to computers.