JLN,
It seems things have gone a bit off topic, but the restrictor seems to only be needed starting in '81.
10a 930 107 289 00
The other piece serves a different purpose. It is not a restrictor, seems designed to allow gasses to flow, but prevents spread of flame due to a backfire. The hose itself works like a PCV, but unlike a PCV valve, gases flow in both directions.
According to the PET, it was used in all the 911-912's from '65-'81
For '81 it was moved from the side of the airbox to the Inside of elbow 47a.
47b 901 107 729 00 backfire grid -81
