That plastic line is the vac feed for the EGR and AIR switch over valves..
They get brittle from engine heat and crack.
Replace with a single length of rubber line and throw the plastic one out..
This line breaks and is the single most common reason for both EGR and Air pump CE lamp fault code on 104 engines .. it is the first place one should look when CE comes on from those two codes [ egr, air]