ok not a 6.2 but a 4.3 v8 diesel that, if you put it on the back of a destoyer would completely cover it in a nice big black cloud...

it starts first turn of the key from cold (after plug cycle) but is really smoky. its a blue grey smoke at idle but when you demand something of it, its really black...i`m thinking that its the pump due to its easy starting so compression must be ok... and seems to have plenty of power, what do you guys think.

ps i got it like this in a Range rover.

The injection pump in the 4.3s was notorious for several failures. Leaks, broken delivery valve springs, stalling advance failure. Pump could be the cause of the smoke at idle, but not the black smoke.
Black smoke means your engine is not getting enough air to burn all the fuel its getting.
Extremely dirty air filter, intake blockage, valve train problem, exhaust restriction, something along those lines.