Check out
http://www.spece30.comI raced a 325i there for two years.
The 318i is legal...but no one has built one yet.
Very restrictive rules...but that is good. It doesn't end up being a checkbook race. Cars with HR race, Bilstein sports, camber plates, offset CAB and some good sways are VERY fun to drive. Spec tires keep the costs down too. (TOYOS).
Good group of guys too!
Ric