sounds to me like exhaust valve guides or seals...?
Valve guides or seals leaking produces blue smoke and is a little harder to see than the white smoke. White smoke definately has something to do with coolant getting into the combustion chamber.
I'm no expert on turbos, but I'd bet something happened with the seals in the turbo. Did you see any cylinders that were especially clean once you pulled the head off? If so, it was most likely the head gasket. I would think if the coolant leaked through a seal in the turbo, the coolant would come out the exhaust, since it's probably under less pressure than the intake side of the turbo. But then again, maybey the coolant just goes through the turbo housing and out the other side to cool the whole thing down and doesn't actually have a seal to the turbine.
