I have set up a procurement profile in SPRO so that each Order type has a different Purchasing Group (we use this field for release strategy). So here you can see the first Order type, and when I create an External, the Purchasing Group defaults to 200:
For the second Order Type, the Purchasing Group defaults to 212:
... but when I procure a Material/Vendor that has a PIR, the Purchasing Group resets to 200!
In the last image, we need the purchasing group to not update from 212 to 200, however that is accomplished.
PIRs are created automatically when a PO is generated, using "Default Values For Buyers" TCode OMFI:
(This last piece is not allowed to be changed)
Thanks,
Micah