ELLBACH-SCHMIDEN, Germany — You may connect PPI Automotive Design, the German tuning house based just outside Stuttgart, with a slick conversion of the Audi TT. But the firm set its sights on bigger and better Audis, namely the automaker's A8 flagship sedan.

The PPI A8 Executive combines good looks with even better performance — up to 600 horsepower in full tune.

Under the hood, PPI offers two stages of performance for the 4.2-liter V8, starting with a modest upgrade to 420 hp. A more powerful variant adds an intercooled supercharger, a redesigned intake manifold, a reprogrammed ECU, a sport exhaust system and a sport air filter.

The results are impressive: Output rises to 600 hp and torque to 638 pound-feet. 0-60-mph acceleration takes less than 4.5 seconds, with top speed electronically governed to 186 mph.

The A8 Executive benefits from extensive suspension mods, including an electronic sport module that lowers ride height on air-suspension models by 1.6 inches. Brakes are upgraded, with ceramic discs available as an extra-cost option. PPI fits Michelin Pilot Sport2 performance tires to its own 20-inch custom alloy wheels.

The exterior transformation is subtle, to say the least. The A8 Executive gets a front spoiler with center splitter, rear apron diffuser and rear spoiler. In addition, the exterior can be finished in matte black or matte carbon fiber, with all exterior chrome deleted.

PPI offers a wide range of interior enhancements; its materials palette includes leather, Alcantara, carbon fiber, aluminum, Kevlar and a new carbon-fiber-etched leather.

What this means to you: Kicking Audi's big bruiser up to the next level, without attracting undue attention from the polizei.