[dontask]

From here:

http://www.e90post.com/forums/showthread.php?t=487328

The E9X M3 brake master cylinder has its own part number. That means it's most likely that the E9X M3 probably generates a different amount of pressure, most likely HIGHER because the E9X M3 calipers probably has a much larger piston area.

Just bolting on E9X M3 brake parts on a run of the mill E9X would actually result in REDUCED brake performance because the E9X brake master cylinder will NOT be able to supply the same pressure the E9X M3 master cylinder can.

On the other hand, the E9X 323i, 325i, 328i, 330i, and 335i in addition to the E82 and E88 135i all share the same brake master cylinder part number. The "best" upgrade available, if you want to stay with BMW part numbers, would be to use the 135i calipers with 335i rotors with a custom caliper bracket.

Or just get an aftermarket BBK that is designed specifically for the vehicle and be done with it.