At 450 PS (444 hp / 331 kW), the latest BMW M4 LCI Competition is the most powerful 4 Series you can buy right now. However, with a little assistance from Siemoneit Racing, the numbers can go way higher.
The most interesting offer is called Stage 3 and consists of SR 700 turbos, downpipes, sports catalysts, a high-flow air intake system, an active-valve exhaust and a reinforced transmission. The resulting 660 PS (651 hp / 485 kW) and 680 Nm (502 lb-ft) of torque are enough to make the coupe sprint to 100 km/h (62 mph) in just 3.7 seconds, shaving a half of a second off the stock time. The top speed simultaneously rises by 35 km/h (22 mph) to 315 km/h (195 mph).
The Stage 2 offers a much more conservative kind of tuning, specifically EWG downpipes and an ECU tune. Even this is enough for a boost to 560 PS (552 hp / 412 kW). You can always cut costs and go for the software-only Stage 1 and still get 510 PS (503 hp / 375 kW).
Prices are pending.