My Merc splutters and coughs and feels like it only running on 1-3 cylinders?

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We have replaced the MAS,2 full 16 BOSCH Platinum sets of new plugs! 32 IN TOTAL! the plugs keep burning out!!!2 new coils were replaced and fulla set of new leads. When scanned the read says " COMM BUS COMMUNICATION FAILURE and LEFT OXY SENSOR"??? .It continously splutters and chugs and every now and then stalls at low revs. But not in full cruise....it just splutters along.When first started and not driven it will idle well but once put through the test...even a short coughing spluttered drive, the idle drops to around 300-400.The fuel pump and pressure is fine, no problem.Exhaust test is fine.If I put my foot down from take off forget it! At full throttle top speed is at times only 50-60kmh. At first this problem was only really happening once every now and then, but once I put it in to get fixed once and for all the problem is 100 TIMES WORSE !!!!! With my research it doesn't seem like a crankshaft sensor position. However it's probably obvious that I am not an expert.... nor is my mechanic on this one.I remember hearing that some early 2000's V8 FORDS in the past had a problem with the 2 computers communicating properly.Could this be a similar problem? How many computers are there in a 2001 ML 430? THANK YOU.