Renntech has a new upgrade for the Mercedes-AMG GT63 4-Door Coupe. It’s called the RIIX (arr-three-ex), and it combines the aftermarket specialist’s highest power upgrade with a functional exterior aerodynamic package.

The under-the-bonnet of the Mercedes, the upgrades take the twin-turbocharged 4.0-litre M177 V8 engine to 1,196 bhp and 927 pound-feet of torque, which is a lot more than the stock 681 bhp and 736 lb-ft of twist from the model. The package includes all-new Stage II high-performance turbochargers, a re-mapped ECU, a carbon-fibre air intake system, high-pressure fuel pumps, and other tweaks.

Gallery: Renntech RIIIx Mercedes-AMG GT63 4-Door Coupe

The car’s output decreases with the fuel type. The 1,100 bhp is only available when using 100 octane gas. 93 octane drops the engine’s output to a still otherworldly 965 bhp and 917 lb-ft of torque. Renntech scaled back the power to optimise performance and drivability.

The engine pairs with the automaker’s nine-speed automatic gearbox, but Renntech installs its Transmission Control Unit and Drive Control Unit. The GT63 4-Door has all-wheel drive and can sprint to 60 miles per hour in 2.44 seconds and hit 100 mph in just 5.5 seconds with the upgrades. It can complete the quarter-mile in an astonishing 9.9 seconds at 139 mph.

Renntech also installs its carbon-fibre aerodynamic package as part of the upgrade. Components include a front splitter, front canards, two-piece side skirts, a rear diffuser, and an adjustable rear wing, which all improve the downforce of the car. The GT63 also wears RIIIx badging and Renntech RPS 10.2 forged aluminium rims that measure 21 inches in the front and 22 inches in the rear. They come wrapped in Michelin Pilot Sport 4S tyres.

No upgrade is complete without a new exhaust system, and Renntech delivers. It offers a stainless steel upgrade that includes downpipes with 200-cell catalytic converters and performance mufflers. The system reduces exhaust back pressure while increasing sound management through the electronically-controlled exhaust valves. Drivers can opt for 100-percent unrestricted sound, perfect for those late-night neighbourhood arrivals.

Renntech says the RIIIx package is limited, with it costing $94,980 (approx. £76,400). That does not include the cost of the car.