there are many more cars that can aerodynamically adjust itself at various speeds... not just the enzo...
mazdaspeed take note that not ALL slap-on spoilers give you downforce... some of them are just dead weights... they have to be in the shape of an upside aircraft wing to be in the least bit effective... as Kaluz mentioned the difference in pressure producing lift, a wing works in the same way... so if you turn it upside down it produces negative lift/downforce...