Actually, the 930 debuted for 1974. The engine was given an intercooler (and other minor updates) for 1976 that boosted power output. In 1980 the vehicle was removed from the U.S. and Japanese model lineups due to changing emissions regulations - Porsche felt that the modifications neccesary for compliance with the new regs would hamper performance and squash interest in the vehicle. It was re-introduced for 1986, producing 280 horsepower, a slight bump over the 260 horsepower of pre-86' models. A *very* small run of 1989 models was produced featuring 5-speed transmissions (prior to this point, only a 4-speed had been available) although they are hard to come by, as Porsche was at this point already fazing in the 964, which meant that the 930's platform was being discontinued. Post-1989 model year Turbos don't use the 930 designation number. The 935 was Porsche's race-car variant of the 930, and a version of the 935 used the famous "Flachbau" or "Slantnose" front end. Porsche produced a small number of street legal
930s with the 935-style "Flachbau" front end, but very few were made and they comanded a huge premium over normal 930s. They can be found today, but be weary, many of them available on the used market had shoddy after-market slantnose conversion kits installed which don't usually look proper and are prone to difficulties.