Tuner Claims Stanced 725-HP AMG GT 63 4-Door Has Perfected What AMG Couldn't

Sep. 23, 2023 4:01 PM ET by John Mendoza Tuning / 7 Comments

But we're not so sure we believe them.

Already a leader among high-performance four-door grand tourers, the Mercedes-AMG GT 4-Door is at the center of a transformation called X290, courtesy of Mariani Car-Styling. This family-owned company has given the AMG GT 63 4-Door a distinctive makeover, elevating its visual appeal and performance capabilities.

Mariani enhanced the AMG GT 63 4-Door's twin-turbo 4.0-liter M177 V8 engine with a specialized ECU remap. This modification catapults the vehicle's power output to 725 horsepower - 148 hp over stock and inches closer to the Mercedes-AMG GT 63 S E Performance's electrified output. Mariani's tune also increased the torque to 700 lb-ft.

To help increase power and give the V8-powered four-door coupe a proper growl, Mariani equips it with a valve-controlled exhaust system, delivering a commanding V8 soundtrack when fully open. The valve control feature grants owners full authority over the pipes in any driving mode - similar to Manhart's modifications for BMWs. The package also adds original AMG diffuser and tailpipes for a sporty look at the rear.

Mariani has equipped an air suspension system that does more than enhance the AMG GT 4-Door's stance; it is there to improve handling dynamics, allegedly, although whether an aftermarket air suspension can hold a candle to the fixed coil-spring setup designed by AMG is dubious in our eyes.

Mariani offers one-piece and multi-piece forged wheels in various sizes, ranging from 21 to 22 inches. Each wheel and tire combination is designed to ensure a precise fit down to the millimeter without additional wheel spacers.

Meanwhile, the "Mariani SuperSport" wheel and tire combination boasts the widest stance, with dimensions of 11j and 12.5j x 21 inches with 325mm tires, filling the wheel arches with muscular presence. While not among the iconic aftermarket wheel designs, the precisely measured tire clearances allow the robust wheel and tire assemblies to integrate into the bodywork with minimal alterations.

Mariani didn't disclose the pricing for its AMG GT X290 tuning package, but claimed to have "perfected the AMG GT 4-Door." Maybe we have different definitions of perfect.