White smoke - Coolant
Black smoke - Turbos, Valve Stems, etc.
Blue smoke - Gas

I would be worried if you have white and black my friend. The smoke you see coming out from SeaFoam is all the carbon your engine has built up over the span of its life. Thats good to see shit come out. Also, the turbos may have been rebuilt, but a non-ball bearing turbo will never be "perfect" again even after being rebuilt, and if its rebuilt by some jackasses, than it REALLY wont last.

Good luck sir.