It starts with visual and aero changes using plenty of carbon fiber. An M Performance splitter, spoiler and rear diffuser work together to reduce lift. M-branded side sills, tailpipes and mirror caps round out the modifications you can see on the outside. The tailpipes are said to be especially resistant to corrosion as they're made out of titanium and carbon fiber.
On the inside you get an M Performance steering wheel with carbon fiber shift paddles — BMW just told us the U.S. won't be getting a manual 330i or M340i. There will be even more carbon fiber trim throughout the interior with special M Performance floor mats as well. Moving on to the brakes, we get upsized rotors that are perforated and grooved. BMW's press release says they are 18-inch front rotors; that is obviously wrong (largest in the world are on the Lamborghini Urus at 17.3 inches). We contacted BMW and a spokesperson confirmed the mistake, but we're still waiting for official figures. Four-piston calipers made of aluminum and painted in red clamp down on those larger rotors. There are 18-inch or optional 20-inch wheels available too.
BMW also included a data and video recorder to be used on the race track. Plug a stick into the OBD port and it'll record everything you might want for post-racing analysis. There's no pricing for this M Performance package yet, but the new 3 Series goes on sale in March 2019.