The M57 platform can suffer from valve float under higher boost and power levels. When running high boost pressures (35+psi), these performance springs increase the seat pressure which reduces the likelihood of valve float.
 
We recommend changing the springs for applications above 280hp. Not only are these springs stronger but they are also new, so a great upgrade on old, tired springs.
 
Can be changed along with the valve stem seals without removing the cylinder head.