I'm currently putting 335i calipers on my 128i. I wouldn't do it until I confirmed that I wasn't altering the OE brake bias. I know all too well about the negative effects to ABS function and performance that are brought about by altering bias. Driving additional forward brake bias will also increase understeer on corner entry through the trail-braking phase, for those of you who are driving on tack. Upgrade wisely.
For those who need credentials: 5+ years engineer in OEM vehicle performance development, 4+ years as a professional development and race driver.
128i vs 128i Performance vs 335i Brake Bias Calculations