The factory wires are fine provided they are in good shape and you are running a standard head unit. So if your vehicle is a 1988 monte Carlo you might wanna replace that old *** brittle wire, but if its a 2000 Lancer you should be fine. As well, if you are putting in an amp thats 50x4 RMS, I dont suggest tapping into the factory wires, I would run my own. Does that help any?