We've seen the mysterious BMW M4 a few times now, but we are (almost) certain that it's the track-focused BMW M4 GTS. The lightweight variant of the coupe is wearing "Safety Car" decal but that is likely just an alternative form of camo. The huge rear spoiler, pronounced chin spoiler, bigger brakes and lack of rear seats all point to this being the M4 GTS, which has been spied here testing in the snow. Where the M4 weighs in at 1,572 kg, the GTS will weigh less than 1,400 kg, and come with around 450 hp as well as a more track-focused chassis.