My car hasn't had "long term" track use yet, but so far so good. Just replaced the pads and fluid/ss lines and pulled the front pins and it drove great on track. I bought KW CS to make it quicker and more fun to drive on track, but it is not at all a necessary mod. I personally think the M3 needs at least some good street tires (AD08 or similar) if you drive hard too, it is heavy and powerful and overheats PS2's really fast. Driving in the instructor/advanced group at Barber I got the tires so greasy it became a slip-n-slide after only 10-15 minutes.
Are there upgraded oil cap seals? Mine too is beginning to leak after only 30k miles of street use and ~500 track miles.