Jeez, it could be a whole bunch of things if you are only able to pull the generic codes. I have a 2007 ML 320 CDI with over 200,000 miles. I bought it for less than $7500 and put about 1,000 miles a week on it.I think I have replaced just about every common sensor chasing some of these codes as I usually try to fix things in my driveway. Knock on wood, mine has been behaving for the better part of the last 50,000 miles. I would check for air leaks associated with the MAF horn that feeds the turbo. It is common to have small leaks with the air intake cause a LHM condition. One time with mine the plastic engine cover wore a hole in the top part of the horn and that was enough to put the car in Limp mode. I remember once towing a trailer back from Indianapolis, about 1000 miles, needing to clear limp mode with my reader after losing boost and thinking I split an intercooler hose but in actuality, the car puked out the MAP temperature sensor which I could have fixed with a zip tie had I known. For a while, I was having issues with the pressure sensor just after the turbo getting carboned up that would throw me in LHM but that’s not happened for a year or so. I have a Foxwell NT530 scanner which has been pretty good but even that has limitations.