Originally Posted by bradleyland
When we look at the M135i, the engine is a vanilla N55 with a different software package. That I'm aware of, there are no physical changes to the engine internals. This is the case for all MXXXi models. The engine is a production variant with some minor changes; usually software.
So, the engine in the M135i may be designated as an "M Performance" engine, but that is a marketing label only. The enthusiasts here on Bimmerpost prefer to look at what the engine actually is, rather than what label is assigned to it.
You are incorrect in that assumption- The M135i has a forged crank and different rings additional cooling and of course software. There will more to the next version.