SeanC
I apologise for not responding sooner. I missed your post and won't bore you with excuses.
I've not followed up on the smoking issue - the transfer box replacement knocked a hole in my budget so I'm holding fire on what might be an expensive turbo fix.
I did talk to a non dealership BMW bloke and he mentioned turbo,valve seals, etc,but without taking the car in he couldn't be sure.
Again, I'm sorry for leaving you hanging.
R