Slamdit,
You only need to connect the wires to the plug at the firewall, not the ECM. I did this in my 08 Aveo 5 and it works like factory cruise. I used the negative wire from some speaker wire I had that had small spade connectors already connected and put shink wrap tube on them for isolation. Connect them to the 2 outer pins as the post says and then connect to the two green/white wires at the plug and presto, cruise control.