My guess is three turbos. Two up stream, and one down stream.
Originally Posted by Diver
I enjoy looking at these renders. My personal belief is the new M3 will look like a reduced size M5. My bets for the engine are 3.0 liter, 2 bar of boost, large twin scroll turbo, electric supercharger for low end oomph and the new part of the valve gear will be cylinder deactivation. I don't have inside information, just guesses.