I don't see why you would want 255's on the front, it will kill the steering feel. Rides great on my setup and I'm sure would cope with tuned 135i power. In fact the garage that did it have a 380bhp 335i demo car on similar setup (but 20" wheels, for press attention really rather than handling)
Pirelli 245/30 ZR20 front, 285/25 ZR 20 rear
http://www.birdsauto.com/1-PDFs/E9209920100.pdf
Will be of interest to anyone looking to tune a 135i 