K-Bus is for the VW diagnosis. Do not use.
GA is for GALA (GeschwindigkeitsAbhängige LautstärkenAnpassung), this pin is connected to the speed sensor to adjust the volume automantically. be careful not to ground this since it could cause the abs to malfunction.
S Kont is for switched plus

Please read all the other threads about original VM car radios on this boards that topic has already been discussed to death. j