[Guru]

Thanks Clan, however I seem to remember seeing a video of a guy pulling out the Y shaped TB of a 2007 2.0D and showing 3 snapped teeth off a cog wheel inside...

Marmoset> If there's a lot of oil residue inside then both the temp sensor and MAP sensor are bound to be covered in oil too, which may lead them to report inaccurate readings, and this too may be causing your revs fluctuations.

The temp (green) sensor can be inspected visually by pulling it out after undoing one torx screw.
You'll see nothing by pulling out the MAP (black) sensor except a small black hole... after all, it's for measuring vacuum in the system.

Back to your Q about oil residue in the TB> as you may have noticed, there are two entries: one small entry through that aluminum pipe coming from the EGR, the second larger opening is from the turbo via intercooler.

If the residue is only oil, and a lot of it, then I would suspect a failing turbine bearing, and the intercooler is bound to have loads of oil in it too = worst case scenario ... does your car smoke on hard acceleration? do you need to top up oil once in while?

If it's a moist black sandy like substance aka soot, then it's coming from the EGR valve which may be sticking in the open position causing too much exhaust fumes to enter the intake manifold... this also causes rough starts and or misfires, or may cause the car not to start at all.

You have some investigation to do.