The Porsche 991 GT3 (or simply the Porsche 991), is a high performance compact sports car primarily manufactured by Porsche for racing events. It is named after the FIA Group GT3 class, which it was designed to compete in.
The 991 GT3 appears in MF Ghost in the form of a Carrera 991 GT3 as the car of choice for Ishigami Fuujin, the number one driver for MFG. It appears to have been heavily modified, as stated in the manga, and has a colossal amount of horsepower and handling ability, as it was specifically designed for such racing events.
The No. 1 Porsche 991 Carrera GT3, driven by Ishigami Fuujin./First Appearance (Chapter 4)
A distant front view of the GT3. (Chapter 4)
A close up, more detailed front view of the GT3. (Chapter 4)
The Porsche appears twice in the manga, once in the form of the 991 Carrera GT3 as car number 1 (driven by Ishigami Fuujin); and in the form of the 718 Cayman S as car number 12 (driven by Mikhail Beckenbauer.)