Mk3 TD diesel injection
 

Just wondering if anyone has a drawing of how exactly the induction system and wastegate works on a Mk3 golf Turbo diesel (AAZ not TDi)? Mine is feeling quite sluggish, can't hear any turbo whine, seems to put out quite a bit of black smoke even under mild acceleration, so thinking it might be running rich. Fuel economy still seems pretty good though so maybe wastegate is not working properly so i am not getting any boost pressure. Noticed there is what looks like a sensor of some kind on the diesel injector pump right in the centre of the four fuel delivery pipes that has some wires coming off it. these look as though they have been repaired at some time in the past.Has anyone got any idea what this is?
hope someone can help.