Hi. I bought an ebay wiring harness that was supposed to be for my 2003 wrx, when it arrived, the plug that goes under the rear right hand passenger seat has a different plug shape, a few different coloured wires, and one extra wire. Two of the wires, Black/yellow and Black/white have their own independant plug that was built in on the original plug. My biggest issue is trying to ID the plug that came on the ebay harness so I can ID wires to match up. Pictures will be posted. Let me know what you think.
https://img.nasioc.com/image/hqnDj
https://img.nasioc.com/image/hqoOI
https://img.nasioc.com/image/hENms