[mjannusch]

Yes, you need to hook the green wire to the ECU side of the factory EGR wire that you unhooked when you removed your EGR valve/sensor assembly.

You can determine which wire to connect to at the EGR connector by using a multimeter set to measure ohms and connect it to the right pin at the ECU and then hook the other end to one of the wires at the EGR connector. When you find the right one, the meter will show 0 ohms or very close to zero. Otherwise, look at the wire color at the ECU for that pin and see if there's one at the EGR connector that matches the colors.