my M.benz c180 engine faulty some times?

can any one help me ,my mercedes2000 c180 w202 some times while driving makes engine faults(fauling in one spark) missfiring;just restart the engine and it become very smooth good normal car;I changed the spark plugs ;the 2 igntion coils;also the airflow meter;
I always feel after4 days of changing fuel&air filters it has a lean mixture and make bombs sound!!