Google answer 1: http://www.thehoffmangroup.com/c/air.../2008_Bmw_135i
Google answer 2: http://www.ecstuning.com/BMW-E82-135...pose/Air_Ride/
didn't search any more, but you get the idea. both these look like about what you'll get on any market for our cars. BMW is the ultimate performance machine, not many buy for sitting on the ground. hoffman group looks complete where ECS you'd have to piece it together yourself.