AIR pump - run rich to reduce combustion temps and NOx products, then inject fresh air into the exhaust to complete the burn
EGR - pass inert exhaust gas back thru the intake to lower combustion temps, again to reduce NOx products
Both of these emissions techniques were being employed about this vintage. I don't know if this is the answer, just suggesting it may be related. I do know I have seen early '70-ish intake manifolds with EGR hardware. I have seen AIR pumps too about this vintage but don't recall if it was on an inline.
