Good maintenance is most important. Flush the engine oil & change every 6k on a diesel if you are using mineral oil. Best to use a synthetic oil if changing every 10k. I recorded a video at Mobil Uk when synthetics first came to market & they showed us a cylinder liner from a truck that still had the manufactures hone marks after 100k!
It is the carbon that fu**s everything up.
I have used an oil additive called Amtech, it has rave reviews & I am converted to! I can say I noticed the difference in the performance of my old turbo rover (peugeot engine) within two hundred miles or so. & It now goes in all my cars.
There is a turbo cleaner on the market, I have not tried it yet, from a company called Innotec.
http://www.innotecworld.com they produce a vast arange of industry cleaners, Lubes, sealers, paint etc. The turbo cleaner is easier to find on the uk site here: http://www.dieselturbocleaner.co.uk/
Then there is Xado oils that have the TUV certificates, these do the same as the Amtech known as nano technology. Again I have not tried this one but they do a restore & prevention solution for diesel pumps. Maybe this is the one for the dci owners.
"This XADO product is specifically formulated to restore the internal workings of HPFP (High Pressure Fuel Pumps). It will also provide vital future protection against wear and tear. If you want to maximize the potential of your engine, you should also revitalize your fuel pump."
http://www.xado.co.uk/engine_treatment_oil_additives.htm If it does'nt cause any harm then it's got to be worth a try.
Just my thoughts!