Might be dirty/plugged injectors....tried running some injector cleaner? Redline SI-1 and Chevron Techron are good.

Our 300E has run smoother and smoother and mileage gotten better and better after running a few tanks with Redline SI-1 in it. It idles so smooth you can't even tell its running! As an experiment I have now switched to using V-Power gas instead of running Redline....to see if its just as good.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)