I found this product through google and wondered if anyone had used it?

Its called Carbon Blaster and its found at the bottom of this page:
http://www.dieselbob.co.uk/fueladditives.shtml

The website has some info on diesel engines that seem sound advice?

RUNNING ADVICE

Engine Oil

Over the years we have had the opportunity to test various engine oils on many vehicles.
Fully synthetic oils are ‘pushed’ as the ultimate choice but we beg to differ.
Fully synthetic oils are too ‘thin’, this results in oil leaking past valve stem seals and past turbo seals resulting in blue smoke at start up and oil in inlet/boost pipes.
We personally use and advise that a semi-synthetic oil is used with a rating of either 10/40 or 15/40, these oils are more viscous and are less likely to weep past seals. These oils also deaden engine ‘tapping and ticking’ sounds.
We have yet to decide the best oil, but will add this info at a later date.
Air Filters

A clogged or partially clogged air filter will create an all manner of problems such as power loss, black smoke, reduced mpg figures, failure of the MOT smoke test. It is imperative that the air filter is renewed at the recommended service intervals and more often than recommended if the vehicle is used in dusty conditions (not normally a problem in the UK!).
We strongly recommend using either a genuine replacement filter or one from a reputable manufacturer, like everything these days dirt cheap parts are available but cost cutting engine parts is false economy.
Also, blowing out the air filter with an air line really is not a good idea.
EGR Systems

EGR (Exhaust Gas Recirculation) systems where added to the diesel engine to reduce exhaust emissions when the engine is idling or under partial load. Exhaust gas is dumped back (via a valve arrangement) into the inlet manifold where it is again ‘re-burnt’ and in theory cleans the exhaust gases. An excellent idea in theory and on paper BUT once the engine has been in service for a few years the EGR system and inlet manifold become caked in soot reducing air flow, increasing emissions and reducing power and mpg figures. Once the problems manifest themselves it is recommended that the EGR parts and inlet manifold are removed and cleaned (steam cleaning and physical scraping) to remove all the carbon and gunk. There are ‘wonder aerosols’ available that claim to clean out the EGR system. These aerosols have very limited effects and have the potential to cause damage (though our non caustic CARBON BLASTER has proved very impressive without damage). The only way to do the job properly is to remove the parts and ‘get involved’. Deactivating the EGR system is another option but not all vehicles will allow this to happen as the engine management light will illuminate.