The line I would take in an E90 M3 would be a little different than in my 330. First, the e90 can't do a quick switchback like an E46 with coilovers can.
At MSR Houston, I did a 1:47:6 in my 330 @ 3320 lbs. I did a 1:45:5 in my E90 M3 at full weight and stock damper, dinan springs, stoptech BBK.
Make no mistake, a well driven E9x m3 will slaughter a non-m e46. Just wait until people start putting coilovers on AND dropping 400 lbs...those will be absolute beasts.