 Power output varied by model year and market, but 900S and 900 Turbo models produced after 1985 were fitted with a 16-valve engine, while the basic 900 kept the earlier 8-valve engine.Some modern Aero-model Saab cars featured only a slight increase in performance, such as the Saab 9-3, while other models featured a dramatic increase in performance, such as the Saab 9-7X.The base 4.2i 9-7X produced 285 horsepower, while the Aero model produced 390 horsepower.