I recall having serviced our company diesel SUV last year. The problem with that SUV was the rev being unable to cross 3,500, and thus cruising at the maximum was limited to 90 km/h!
They changed the fuel regulator and a few other components and it was all fine after that.
Don't know if it works the same for a Benz.
126 tailed by a 203, 129 leading the pack.