Funny to hear all these butt hurt M3 owners have the need to explain the M3's performance before congratulating the M135i...
http://fastestlaps.com/comparisons/b...m135i_f20.html
I am not sure where this data comes from but a quick search shows that in stock form the M135i is within one second of the M3 on several different tracks.
A 500$ canned tune on the M135i evens out the power between the two cars, with the M135i keeping its weight and torque advantage. I think it's pretty clear what happens then....
Damn impressive.