excessive black smoke W638 108cdi

[tebelee]

Hi there Ive got a 2003 108cdi W638 Vito van and the last couple of days I've noticed excessive black smoke out of the exhaust when accelerating.Also a couple of months ago and less than a 1000 miles I had the injectors reworked and new air and fuel filters and flew through the emissions on the mot test.
Any ideas please?
Thanks in advance

 

[Auto-mobile]

Any lack of power? A leak in the boost system can cause excessive smoke, is you mpg down? If you suspect injectors your mpg will probably plummet.

 

[tebelee]

Hi, Theres no lack of power, and the mpg seems as normal. Wheres the boost system on the engine?
Thanks for your help.