It always seems like the ones who are very focused on making their car faster on the street have never taken their car to the track. I highly recommend doing that. The M3 is plenty fast at the track stock (way beyond most of our skill levels) and after track experience, driving fast on the street is hardly any fun at all, not to mention you start to see how dangerous of an environment it is for that kind of driving. I don't even find driving on the mountain back roads very fun anymore. ISF's and C63's try to egg me on all the time and I just cruise at a comfortable pace thinking about that next track day why they make themselves look like an idiot in traffic.
(1:40 @ Laguna Seca, 2:03 @ Thunderhill, 1:56 @ Infineon)