A bad PCV valve can put oil in the intake tract - if one of them does not close during positive manifold pressure it can blow oil into the turbo inlet duct. I think that it would depend on how much oil is in there. A small amount with some residue on the charge pipes is normal - a greater quantity would point to turbo seals. You said there was no burnt oil in the exhaust - where is the smoke coming from that you reference above ("little bit of smoke coming from the turbo...")?