My code reader tells me the "O2 sensor is malfunctioning, bank1, sensor 1" and that the "Cylinders 1-4 are misfiring." Well, I have replaced the Bosch O2 sensor twice and all 16 spark plugs. There must be something I am missing??

Has anyone had this problem or know how to repair it??
2000 ML55 AMG.
Thx.

 

sorry, im going trough the same problem I even change the cat converter... help!!!