I do not know that this will be of help or not. I was at the junkyard ans saw an 82 300SD from which the IP was apparently removed without removing the Oil Filter Housing. Next to the car I found the Vacuum Shuttoff from the IP (which as it turned out was no good; would not hold vacuum). I believe that the Vacuum Shuttoff was removed from the IP so that the IP could be removed without removing the OIl Filter Housing.
In any event the IP was gone and the Oil Filter Housing was not disturbed.

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84 300D, 82 Volvo 244Gl Diesel