Hey guys! Sorry to resurrect an old thread.
I too have an '18 Limited BRZ and purchased a CCS loom harness to hook up with my Kenwood DDX919WS.
I've got everything finally working after troubleshooting the USB ports and camera issues.
I have both cameras working (both front and rear since the HU has outputs for both) but I'm getting a scrolling static image - the front camera displays a ghosting image of the rear and the rear display a ghosting image of the front.
I've checked all my connections and even tried a couple of different grounding points.
Have you guys fixed your issues? I'm wondering if I need a 12v relay/filter/capacitor to attempt to eliminate the static issue?
Example videos: