In 1981, Porsche introduced the 'flachbau' option, commonly known as the Slantnose, for the 930 911 Turbo. It featured a flat nose reminiscent of the 935 Group 5 racecars, most famous of which is likely the whale tail adorned 'Moby Dick'. Fewer than 1000 cars were ordered with the option.
In August 1993, just before to the introduction of the 993 911, Porsche's VRS department decided to give the 964 one last hoorah. Also known as the Exclusive division, it introduced the hand-built Flachbau (German for 'flat construction' or 'flat form'), known officially as the 1994 Turbo 3.6 S Flatnose.
Aside from the obvious flat nose with its 968 style pop-up headlamps, the Flachbau featured several other cosmetic and aerodynamic differences from earlier 964 Turbos. The flat-nose option included exclusive front and rear spoilers as well as different rear fender vents. Those air inlets feed cooling air to the engine and are asymmetrical; the right side being narrower due to the oil tank residing behind the quarter-panel.
The engine in the '94 Turbo 3.6 S is known as the M50/64S. It features specially modified heads, upgraded camshafts, and a different timing gearwheel and turbo. The engine's timing is also advanced slightly from the standard Turbo 3.6, resulting in a factory rated 385hp.
In typical Porsche fashion the Turbo S package commanded a $60,179 premium over the standard Turbo 3.6's base price of $99,000.
Total production for the 1994 Turbo 3.6S was 93 cars, of which 76 featured the flat-nose. The remaining 17 are known as 'package' cars, which carry all the Turbo S modifications apart from a set of regular fenders and headlamps. Amusingly, flat-nose 964s sold in Japan featured pop-up headlights carried over from the 930 slantnose - 10 of these cars exist.
For more in-depth technical knowledge and to learn more, visit flachbau.com, a site dedicated to documenting this rare car.
Other sources: Porsche 930 info (Wiki, deal with with it) and the images.
The Lesser Known Slantnose