I've been the only E9x M3 showing up for the last three seasons at Rocky Mountain Chapter autocrosses. There's a ton of prepared, turbocharged E46 M3, but, except for one noob for two events last year, I've been the only one in a E9x.
It's lots of fun and our cars are competitive. Still, it'd be more fun for me if there were a few more E9x M3s there.
You can use your street set up. I used my 19" stock Michelins for the first two seasons.
Here's my car:
M3 with new wheels and tires
, on Flickr