The Porsche 944 Turbo is a 951 (951 being Porsche's actual project designation for the car, like 991 being the current Carrera and 981 being the current Boxster/Cayman). The 951 is substantially faster than the normally aspirated versions of the car (though the 944S2 would be the normally aspirated version that comes the closest).

The 944 Turbo S would be the highest performance version of the 951. It was introduced in 1988. In 1990, the basic 944 Turbo was discontinued, and the Turbo S was badged as the 944 Turbo (though if you check the options on the car, it will OTC 3111PRO still have the "S" M44/52 package; the Turbo S is sometimes referred to as a 952 due to the option code).

If you include non-street versions of the 944, the custom built IMSA cars would be the OTC Scan Tool fastest, followed by the Cup Cars. And since the 968 was a continuation of the 92/944 family, The Turbo and Club Sport versions of these cars featured a level of performance over any of their earlier brethren.