[sniper]

First, what color is the smoke? As a general rule, black smoke = fuel, bluish smoke under boost = oil , white can be coolant and or oil.

I'd be looking at the turbo first. The likely hood of the rings passing oil is less than the turbo pushing oil.

You might be able to pull the turbos and see if you have coking on the hot side housing at the inlet or any sign of oil there and then check the outlet side to kinda of get an idea of where it's coming from, if it oil smoke anyway.