Right, I think we have got to the bottom of this. Everything put back to together and sadly the excessive smoke is the same. Customer drove along the motorway and the driveability is excellent but the smoke is only present when driving in too low a gear in traffic or stationary at about 2500 rpm when it is very excessive. I noted in my first post that airflow at 2500rpm (stationary) was 560 mg/injection but although todays subsequent test shows exactly the same at those revs, it did climb rapidly after the smoke and misfire subsided. Now the theory is this: The customer undertook an engine flush whilst changing the oil and filter and also ran diesel through it as well. We suspect it removed the sealing around the rings and bores. This can be borne out by how the smoke decreased when he put the thicker 10-40w oil in after the initial 5-30w. We suspect that the engine misfire also contributed to the blue/black smoke which is a mix of unburnt diesel and oil.
The way forward: Customer is going to keep the car as it is initially but will add something to the engine oil (any suggestions?) to help seal the rings etc. Because he is fastidious with his vehicles, he will most probably strip the engine down for a re-build after Xmas.
Obviously, I will post any further developments if and when they occur.
Many thanks for the many responses and interest.
Regards
Pete M