if your oil level is to high, the oil wont drain out of the turbo well, it will pool in there and work its way into the compressor side of the intake and then work its way everywhere else.
Same if you fit a BB turbo without an oil restriction - to much oil pools.
if your seals are on the way out, it will do that anyway, regardless of oil level/pressure - this is when you need a new turbo.
catch can - this stops the intake sucking in oil from the oil/vapor that is pulled from the PCV valve from the top of the engine.
Take of your piping, clean it all out..dry it all out properly and then reconnect it.
Install an oil catch can, or oil vapor catchment system.
Drive the car for a while, regularly check for residue.
Its not uncommon to see an oily residue after a while - but excess is something to be concerned slightly about.
if your still getting oil in the pipes after this, your seals are properly leaking and its time to decide
1) keep driving it - it will properly last a long time, until the seal is gone and the turbine shaft clips the outside wall and eats itself up and throws metallic pieces into your engine, causing it to die.
2) replace turbo / recondition turbo