Since the car is new to you, and you didn't say whether you've previously owned a 617, are you sure this is not just normal diesel smoke?

Do you get the same amount (and color) of smoke under very gentle acceleration as under heavy acceleration? How about when you're at 40 mph or more and floor it so the kickdown switch engages?

To your oil leak question: How much blowby do you have? If you take the top cover off the air cleaner housing (engine off) and look inside, is there visible oil? If so, this can drip into the U-tube and be sprayed into the intake manifold by the turbo. But even then, some on this forum maintain that would contribute to a fouled manifold, but not necessarily smoke.

An oil leak inside the turbo itself (from the front oil seal) seems unlikely, and probably wouldn't be of any significant volume.