One additional model year change besides what
asbrr mentioned is that up to 2010 135i models... the rear springs were progressive... meaning as the spring compressed the spring rate increased. This tended to make the car twitchy. From 2011 model year.. the rear springs were static(linear) spring rate.
IF you want I could look at the paint dots on my US 135i springs seeing how I just installed Bilstein B12's and Eibach springs. I'm pretty happy with that setup for the street.
Dack