carbon on plugs

[joe d]

just replaced plugs,coils and plug wires on 2000,c230komp. found lots of carbon on plugs. i have been getting rough idle and shakeing at morning start up. smooths out but does not go away after driving awhile. starter has been making laboring noise also. have a new battery. motor mounts are good . o2 sensors are original. 90,000 miles. MAS replaced about 20,000miles ago.no check engine light warnings. ran ok for a day after tune up. then back to roughness. ECM a possibility and where is it on this car? Thanks