A K1 kit is an assembly you can get from your MB dealer. It consists of a two plastic pieces that fit together and a spring that installs in the valve body. If you are having flaring from 2-3 then more than likely this will solve your problems. Do a search on K1 kit - it will give you all kinds of info. One thread even gives step-by-step info on how to remove/install the K1 kit.