At the turn of the new millennia, BMW
introduced the E46 M3, renowned for its 3.2-liter inline-six that produced 343 horsepower, making it the most powerful naturally-aspirated engine ever built by BMW (the engine it built for the McLaren
F1 notwithstanding). In 2007, the E92 M3 arrived sporting a completely new look and a 4.0-liter V8. The tuning world has been delivering aftermarket packages ever since, and when the fifth-gen M3 (F80) arrives in 2014 powered by a 450-hp turbocharged straight-six, expect more of the same. In the meantime here's four of the best we've seen over the past year.