Hey Fred
I know im late, but I am interested. Did you find out what caused the smoke?
My 2001 330d also smoked black like a coal train, and it turned out to be because of a huge intercooler pipe leak.
Btw blanking the swirl flaps does not cause any problem. If anything the car performes better in my experience 🙂
I also reccomend removing the EGR valve.
Regards