I have the same M119 4.2L engine in 1999 S420. Once I had my check engine light go off, they found that the ignition coil and spark plug on cylinder 8 were inop. If I were you, I would run to a mechanic. If your maf sensor is broken and you leave it alone unfixed you will destroy the cats, o2 sensor and eventually motor. Check Engine light is once there is two occurences of the problem. Do yourself a favor and go to a mechanic.