This 1991 Porsche 964 RSR was built by Patrick Motorsports in Phoenix, Arizona. The engine is a twin-turbo flat-six from a Porsche 993 increased to 3.8 liters. It made 540 horsepower to the wheels on low boost from two K24 turbochargers and 91 octane fuel. The engine features Mahle pistons and cylinders, Pauter connecting rods, GT2 Sport camshafts, custom 321 SS headers, and MoTeC M600 ECU. Power is sent to the wheels through a 993 six-speed transaxle with a Wavetrac limited-slip differential.
Source: Patrick Motorsports (project page)