1974 117 cylinder head question

[h20ham]

I am wondering what the cylinder head ports which are below and to the sides of the intake ports.
They return into the intake plenum, and mix with fresh air.
My guess is they remove the excess combustion
But maybe they are from a high point in the exhaust ports
Hope the photos show up
Yellow spots show the location
Cheers

[h20ham]

m117 cylinder head smog pump bores - Mercedes-Benz Forum

I presume routing the smog ports to a catch can to be the best solution
Any comments please

[Frank Reiner]

h:

The purpose of those drillings is to allow air from the "smog pump" to be injected into the exhaust ports. The air feed channel under the intake ports is supplied from the pump.