Fictional version designed by Beto FR (Kunos' Cayman as base):

The Cayman BFR is a hypercar based on the Porsche 981 Cayman, which has the visual design and aerodinamic concept of the last 911 GT2 RS to fit with the Porsche's sport division look, and other new elements to bring it to a completely new level in terms of performance. A revised package and settings, makes posible a lap time under 6 minutes and 40 seconds on the full Nürburgring, positioning the Cayman BFR as the fastest street legal car, beating the Aventador SVJ record by a 3 seconds margin. The first revision of the car makes it a bit faster now, comparing to the first version which made the same time than SVJ.

The engine, chassis, suspensions, brakes and aerodynamic design of the Cayman BFR are new and configured to get the best driving dynamics.
It is powered by the 4.8-litre V8 biturbo engine mounted in the 918 or Cayene Turbo, but now with 765 hp (571 kW) thanks to many modifications in different elements, like the turbo, exhaust system, admision, or cylinder head, among other components and new materials. Its power is transmitted to the rear tyres by a new seven speed secuential gearbox, specially designed for this car.
The Cayman BFR accelerates from zero to 100 km/h in less than 3 seconds; its top speed is arround 330 km/h, not very high due to the drag generated by the huge aeropackage, which produces more than 900kg of downforce at 300 km/h.
The chassis subframes consist nearly entirely of new carbon fiber and aluminium elements. Also the body panels and other parts are made in carbon fiber and composite materials. The car is much wider than the Cayman GT4, but it weighs around 60 kg less, even with the bigger engine.

As a mid-engine super sport car you have the best handle and dynamics. With tons of diversion and performance at once.

With slick tyres can be faster than a GT3 car on track.

Note:
For realistic performance challenging the real times of the Porsche (991) GT2 RS and Aventador SVJ at Nordschleife, use semiclick tyres, with stock setup, and 30 litres of fuel.