But it will not smell like oil or have an oily feel.

One test to do is to let the car sit overnight and then have someone start it while you are back at the end of the tail pipe with a white sheet of poster board.

Let the exhaust run on the board until it clears and then examine the board. There will be water, which should be clear, and there will be some soot, which should be very black, and that is all. If there is an oily residue it is time to consider the brake booster or the valve guilds. If the water has a greenish tint to it then you have a leaking head gasket.

By the way, the only way the brake booster can be letting fluid leak into your intake is if you have a failure of the booster AND your vac pump. Since this is a diesel and develops no vacuum you would have to be pulling the fluid in through a very worn system.

QUESTION>>>>> When you shut off the car does it run on for a bit? If so you might have worn rings that let engine oil pass the piston rings and settle into the combustion chamber. This is not common, but when you wear out a set of rings in a diesel engine it is possible, and this could also be the source of your smoke.

However, worn rings normally smoke all the time.