Nowt to worry about all vehicles with closed crankcase breather systems have oil in their inlet pipework/intercooler etc, its most likely NOT your turbo at fault, everyone jumps on that bandwagon, what is most likely is your engine is a little tired and suffers a little blowby which in turn allows oil mist to exit via the crankcase cyclone breather and this in turn vents into the air filter pipework BEFORE the turbo, the oily mist then goes through your turbo causing mild panic! and this is where your oil is probably coming from.
I ran my breather to atmosphere to stop this happening.
Dont fit an oil catch tank as they are a pita requiring constant draining down.