TD4 Running rich

Hi. After resolving a myriad of issuettes with my TD4 it passed its MOT today. The mechanic said that it passed the emission test but in his view was running quite rich.
The car has never used so much as a drop of engine oil between services whilst I have owned it, but there has always been a smell of unburnt fuel and smoke coming out, much worse on idle, that is blue and as I said, it isn't the engine oil as it hasn't ever lost any!
I was tempted to change the MAF Sensor as I have already swapped the old Crankcase Breather with the centrefugal BMW unit.....does anyone have any idea what I might do to stop the rich running?

Do your injectors need servicing? How old are they, have they ever been replaced?

Hi. Many thanks for responding. I'm not sure how old they are though I suspect that they will be the original ones and unlikely to have been replaced. Is servicing them something I could do at home or is it a garage job?

Try running a few tanks of injector cleaner (diluted of course) thro' it may help and is a cheap fix to try for injector problems. It may take a few hundred miles to show any real benefit but will certainly do no harm.

TD John - Will do, many thanks. Regards, David