GormZ3 makes a very good point about the SCCA classes for the 1.9 and the M Roadster/Coupe. It is difficult. From what I've seen from my limited time in autocrossing it seems that the most competitive Z-series BMW car in SCCA autocrossing would have to be the 2.8 Coupe. The rigidity of the coupe is somewhat superior to the roadsters and it is much more favorably classed in SCCA soloII. On the other hand, if you are driving just for the fun of it (as most of us are), it really doesn't matter which model you choose. They all have their individual characteristics which make them all a load of fun to drive between the cones.