until 2004. Performance varied from 0-60 mph (97 km/h) times of 5.0-6.0 seconds depending on the source, and a governed top speed of . Twin Turbocharged Z32s also featured adjustable two mode suspension and the four-wheel steering systems called "Super HICAS" (High Capacity Actively Controlled Steering), first introduced on the R31 Nissan Skyline. Nissan utilized the Cray-2 supercomputer to design the new Z32 with a form of CAD software making it one of the first production cars to utilize this tool. Like previous generations, Nissan offered a 4-seater (2+2) model with the Z32. Most Z32s now featured T-tops as standard. A hardtop (Slicktop) model was available in North America, only in Naturally Aspirated guise, and in Japan was available as Naturally Aspirated as well as an extremely rare Twin Turbo model (Japan-only). All “Slicktops” were 2 seaters (2+0). In 1992, a 2-seat convertible version (produced by ASC) was introduced for the first time, in response to aftermarket conversions. In 1990, Motorsports International of Waco, Texas collaborated with Japanese tuning company HKS to create the SR-71 Z32. The cars were upgraded with larger Garrett turbochargers, HKS electronics and a Kaminari body kit designed for the SR-71 by Pete Brock. The SR-71 was California CARB certified and was to be sold through a select dealer network and Japanese performance tuning shops located within the United States. It was planned to build 500 cars per year through 1993. One hundred orders were already in hand. The exact number is not known. The SR-71 claimed the title of the third fastest production car in the world in 1990 for a fraction of the price of a Lamborghini Diablo and Ferrari F40 according to the designer Randy Ball. The base price was $65,000 for the Z32 and SR-71 conversion. In 1995 and 1996, Steve Millen Motorsports (Stillen), developed a SMZ model with Nissan North America that were sold throughout the U.S. and Canada through designated Nissan dealerships. The performance upgrades were covered by the factory warranty. These performance upgrades included: Skyline Group N/GT-R Brakes, which were cross drilled and axially vented rotors with larger calipers and pistons and upgraded HI-Metal front and rear brake pads; a high flow intake system, which added horsepower and allowed the engine to run more efficiently; an aluminized steel free flow exhaust system, which extended from the catalytic converter and increased rear wheel horsepower; and a turbocharger boost pressure increase,