I doubt the IS-F style slide slits make it to production. I hope not anyway.
More than the engine, I'm interested in the stock 4-chassis and what M do to it. From what I've read, the stocker will have a wider and more sporting focus, so with the M increased track and tires on top of that it should grip and grip (and be even
more stable than the E92 M when you don't want it to grip
) Losing even 100 lbs is a real step forward, especially since the 5-er put on another 300.