You did not answer my second question "how frequently has the oil been changed"! The reason I asked it is that it is well documented that the oil used (which ideally should be 5W/40 synt for diesel) in the 2.2Dci (G9T turbo) engines needs to be changed more frequently than the specified 18K / 2 year service interval. Failure to do so is more likely than not to result in problems because oil (other than of the specification mentioned) becomes too "thick" and therefore does not flow so well.

If looked after, (as I have described) this engine will run efficiently for a big mileage and much more than you have done so far. My experience is that the EGR valve needs to be removed and the openings cleaned ~ once a year, especially if you are doing shorter runs, or the engine will start to produce more smoke and will not pull away so well - as you have described. But this is a fairly easy DIY job. Sounds like you have problems with the plastic inlet manifold which has lost its seal somehow as happens occasionally and is also mentioned below.