Save yourself all the hassle and get a BBK in the front. Even with ducting you will just end up burning through track pads at a phenomenal (expensive) rate.
I tried everything with the stock set up before finally biting the bullet and getting 380 Stop Tech BBK in the front. Learn from my experience...
The Cantrell ducts work, but I'm not sure if you need them if you have a BBK. I fitted mine before installing the BBK.
E92 M3, Competition Package, MDCT, Ground Control Adjustable Camber plates, StopTech 380 BBK, OEM exhaust mod