On my 95 e320 m104 Plastic lines: black has slightly larger ID than white w green stripe. Both plastic lines into "Y" hose [into lower intake] from Fuel Pressure Regulator and from gismo that has vacuum hoses to EGR & Air Pump [Electric Changeover Valve ?] were brittle.

After changing them to silicon hose, I started questioning my decision because of the larger ID of the silicone hose vs the plastic lines.

Bob