In 1991, after the end of sport prototypes races, IMSA decided to creat a championship reserved to the supercars of the moment. What a great opportunity for Porsche.

In the IMSA Potenza Supercar championship, the better sportcar were engaged with minor modifications compared to serie and Bridgestone tyres. Porsche modified a 965 turbo 2 engaged by the Brumos team. To accomodate the rules of the championship, the 911 turbo received a roll cage, a 60 liters fuel tank and competition brake pads. The chassis was lowered by 40mm while coil springs, shock absorbers and antiroll bars get stiffer and reinforced. The car also get front air dams in the spoiler for brakes cooling. Some parts of the body were lightened like the front lid.

The 3.3 block received little improvements. With the higher turbo pressure allowed, Porsche obtained 380 hp @ 6,000 rpm and 50 mkg @ 4,800 rpm. An additional oil cooler was added. Like the Group B turbo in 1985, the car was very close to serie standards and weight around 1,630 kg. This important weight was an handicap and for the second race of the car, 1,500 kg were obtained. In this configuration, the car one of the pretendant for the championship victory. And this is what happened. With Hurley Haywood, Joachim Stuck and Walter Rôhrl, the 911 turbo won the IMSA supercar Championship in 1991, 1992 and 1993.