Sooty exhaust smoke

[Kitkat50]

Hi everyone my 2000 2.0 l bongo has started giving out lots of sooty smoke which has a really strong patrol smell, I've changed the plugs (which were covered in soot) the HT lead's and the distributor cap and rotor arm and air filter but still sooty, my next guess would be either the lambda sensor or a leaky vacuum pipe somewhere. Has anyone ever come across this problem before. Thanks
Locked, duplicate post.