Sprinter 313cdi smoking low revs

[Bennijamin]

Hello all, need some help, I have a much loved 313cdi sprinter, its been smoking at low revs for ages, and I can't seem to find a cure, I've had a new turbo last year and 2 injectors done, other two are going to be done, but I'm not sure if it will cure the smoking, it smokes black smoke at low revs or under load up a hill, I can't find a egr valve so I'm guessing it dosnt have one, I've tested the maf sensor and that is fine, so I'm a little lost, another problem I have is a oil leak which I can't seem to find, it's all over the front of the engine and lots of oil under the van too, I would greatly appreciate any help, thanks!