summit racing has a set a eibach drag launch springs, but it says its not for cars you drive on the street, do anyone know why ?

 

Drag racng springs are stiffer on the right rear than on the left rear to counteract axle lift during hard accelerarition. Also the rear springs are disproportionally stiffer in the rear to provide a better plant on take off, same with shocks. Also the right rear spring stiffness is adjustable via an air bag inside the spring. A car with this set up, handles and rides horribly in everyday use.