Really the confusion is that the instruction / picture says if just for fiber optic cables, the other parts is not needed.
Now as you said, both parts are needed to reolocate the OEM HU. So which one is right?
Originally Posted by srcstc
I don't see why there is so much confusion. You are simply extending the connection between the oem radio and the harness in the dash (which would normally be plugged into the oem radio).
Pins 9, 11, 15, 12 and the fiber optic cables need to be extended. it's as simple as that.
One metra harness connects to the oem radio and the other to the oem harness in the dash. So you don't have to cut into any factory wiring. Simple as that.