Hi Stuart, I have had a good look around as white smoke, or indeed any colour smoke is of interest to me, having the same engine as yourself. There appear to be several reasons, although there are many prophets of doom, It could be incorrect injector timing, defective injectors, or low cylinder pressure. You have checked out the injectors, so that can be ruled out. I have come across one comment which could be the cause ---- low quality fuel, which is a relatively cheap fix, and that kind of fix is a good one. I have been advised that supermarket fuel is not the best for a performance engine, and that an occasion tankful of the very expensive performance diesel is a good thing. If the smoke is only on start up it could be pure water vapour, but the misfire seems to indicate something else. I had my car put through thee Terraclean service, basically to check it out and it did a lot of good to the engine giving me 53 mpg on a 90 mile run mostly on a motorway with a 50 mph restriction. Hope this helps, Peter.