BMW seems determined to squeeze out every last bit from the M4. Following the Competition Package and the hardcore GTS version, the Bavarian manufacturer is now testing what seems to be an even more extreme version of the sports coupé. And boy does it look angry!

Spotted at the Nürburgring, the biggest alteration is obviously the elaborate aerodynamic addenda on this prototype. The fixed rear wing on the car is even bigger than the one found on the GTS, while there is large diffuser out back that could easily double up as a medieval torture device. The diffuser, which sits tarmac-scrapingly low actually gives this M4 a rather awkward stance from the rear.

The side skirts are equally jaw-dropping and could easily be at home on a DTM racecar. The front, meanwhile, features a jutting chin spoiler. Curiously, the vehicle sits far too close to the ground, which means that the chances of it reaching production in this form are near impossible.

And that makes it really difficult to pin down this version of the M4.

Our spy’s assumption is that BMW is merely testing the maximum aerodynamic ability of the M4, perhaps for some application on the upcoming facelifted models that are expected to be revealed sometime in 2017. Our guess would be that this could be a tester for the forthcoming M4 GTS racer. These are much closer to their road-going versions in spec, unlike the DTM racecars, which have very little in common with the production cars they are purported to represent. The M4 GT4 can be bought by private racing teams and therefore have to be much easier to work on.

Either way, this is with a doubt the most aggressive M4 we’ve spotted so far.