Hello John (Bruce, Mike, Jeff and others), I am very grateful for all your help and advice with this. Sadly the plot thinkens! After the Specialist worked on the car it was fine for a while. I thought I would just add some RedX treatment (I did double double check it was the correct product) to the next tank full of diesel for good measure. The car was fine for a week or so ........ then I took it for a weekend run!!!!!! For the first part of the journey we travelled in two cars. I followed the BMW at a steady 70 on the motorway for 150miles and a few miles around town. I did notice a tiny bit of smoke from the BMW exhaust when under load (e.g going uphill around town) but nothing to worry about. Later the same day we drove on another 70 miles. The next day I could see smoke - in the rear view mirror - from the exhaust when pulling away from roundabouts etc. It got worse quickly and by the end of that day the car was throwing out CLOUDS of thick BLACK smoke under acceleration - the type of smoke cloud that can be seen by anyone within 400 yards behind!!! I drove the car home steadily the next day. It drives fine, is not noisy, appears to have normal power and is not using oil. Being at a bit of a loss I booked it in with the local BMW Dealer (for a basic £75 diagnostic look) in the hope of getting to the bottom of it. I did give them a full written history of events, but I'm not sure they read it. I have just picked it up and they could NOT tell me why it is smoking now. They told me it shows as needing new glow-plugs (but car starts very well and is NOT at all smokey on startup - so I am not interested in sorting that at the moment). There is no problem showing up on diagnostics re the turbo, EGR or injectors - or anything else. In the end they (the booking in staff) wanted to tell me that taking out the swirl flaps can cause some smoke! No one else has reported this problem so far as I know (and it was fine for a while) and it now smokes to epic proportions (under noticeable acceleration only though). It has a fresh tank of diesel. I am now going to ask my local mechanic chum to just apply his old fashioned (non-diagnostic) mind to it all before I start changing turbos or the like (and may ask him to replace the swirl flaps!). Can any of you make sense of latest problems I am having? (PS: has anyone you know ever welded the swirl flaps onto the spindle they sit on). Confused Fred (Thanks for even reading though all this)