I don't own an M3 but a general rule with tyre pressures that i have found is to start at what the manufacturer recommends then increase/decrease 2psi at a time to find the tyre pressure/steering feel that you are happy with. I guess what i am trying to get across is that there are no hard and fast rules as to what pressure you should run for daily/street driving as long as you don't stray too far from what the factory recommends for your tyre/rim size.
I personally like a "heavier" steering feel so I run Front: 40psi (235/35/R19) and Rear:42psi (255/30/R19).
