I replaced the shutoff vacuum solenoid on the ip (not quite sure whether that was the source of the oil but I've heard it can be).

Yes the above is the source of the Oil.

If the 2 Hoses that go in the Vacuum Shutoff Switch on the Steering Colum Lock are not not connected on the correct Nipple it will not shut off properly.
The solid Brown Vacuum Tube goes to the top Nipple and the Brown Vacuum line with the Blue Stripe goes to the bottom nipple.

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84 300D, 82 Volvo 244Gl Diesel