Stock class, can't change the springs. They have to be the OEM sport suspension that came on the car. So no BMW performance or coilovers.
The shocks however are open, as long as they are double single or non adjustable. They are considered a "wear" item, so they can be changed.
How are the Koni sports on stock adjustment in the rear? I could pick up a set of them from Tirerack for cheap, and just adjust the fronts for balance while leaving the back as is. Gives me adjust-ability in the front at least, and saves money, but is it as good as the FSD's?