Following purchase of an "A" Class 2.8JTD I complained about Turbo Noise to dealer and eventually they fitted noise killer matting. (Noise was a sort of gurgling when pulling uphill)
Matting was fitted to engine cover and floor of cab area, underside of dashboard sited over engine and in addition an engine apron which is suspended at rear of engine itself. I can`t really say I would be overly keen to have to pay for it myself, it might reduce noise a little but you are`nt suddenly going to go into raptures about how quiet it is, the Turbo still gurgled! We also found Tyre Noise to be quite high. We now have an X250 which makes the older 2.8JTD sound like a farm vehicle.
I am about to install some on my Hymer 644 bought from Noisekiller - seems simple enough to install but I am putting in both side of the front dash area and coupled with an engine cover.
Just to put anyone`s mind at rest about Turbo`s following Paapjohns comment (beware those whose sole aim in life is to make negative comments on these Forums) our van ran for five years with no engine problems other than the noise pulling hard uphill. I have owned a Chrysler where the Turbo whistled under load and I gather some Turbo`s do make a noise.