I didn't want mine to always be on with the tail lights or function as a brake light. The wiring for the front fogs are at the main body ecu behind the lower dash panel. It was raining on and off and I was working outside so sorry for the lack of pics of how to run the wire from the dash to the rear fog.
Here's a pic with the connector already removed.
The left & right fogs are on separate circuits, I wired mine to the left hand one. Here is the connector diagram, wire 3 is for the LH fog light, the wire is red with a white stripe. 5 is for the RH fog light, the wire is white with a red stripe. Connecting here will put it after the fog light fuse so no additional fuses are needed.
To remove the dash panel, remove the panel on the side of the dash and remove the philips screw under that panel and the one at the lower right of the lower dash panel, then the panel can be pulled off. For instructions on removing the interior panels in order to run the wire, download the service manual for the FR-S or BRZ, there are great diagrams with locations of all of the clips. There is a factory channel for wiring under the carpet along the door sill.
