With its 4.4-liter, twin-turbo V8 gasoline engine cranking out 617 horsepower and 553 lb-ft of torque, the M8 Competition is the most powerful M car BMW has ever produced. And it could about to get even more hardcore. Our spies have spotted a mysterious M8 prototype being put through its paces on a race track.

Compared to the regular M8 Competition, the prototype is sporting a large rear wing that isn't available for any current 8 Series models. This could mean one of two things: either BMW will offer a special aerodynamic package for the M8 or the automaker is cooking up a track-focused M8 Clubsport model. Chances are the camo is hiding a host of other upgrades, too.

A leaked order guide revealed the upcoming M2 CS will be fitted with a redesigned carbon-fiber roof as well as a carbon fiber center console, door handle covers, mirror caps, front splitter, rear diffuser, hood, and rear gurney flap to make it lighter and more track-focused.

It will also ride on 19-inch lightweight alloy wheels and be available with optional M carbon-ceramic brakes. Other upgrades will include an Alcantara M steering wheel and a modified exhaust system. If BMW is building an M8 CS, we can probably expect similar upgrades.

Under the hood, the M2 CS will also be getting a significant power boost. According to the leak, the M2 CS's engine will produce 450 horsepower and 368 lb-ft of torque – that's a 45 horsepower gain over the M2 Competition. If the M8 CS gets a similar power boost, it could deliver around 650 horsepower.

Also expect it to cost significantly more than the regular M8 Competition, which starts at $146,000. No official details about BMW's track-focused M8 have been revealed yet, but hopefully more information will leak online soon.