The OEM BRZ headlights have the ballasts for the D4S bulbs attached to the bottom of the headlights, so I used 3M tape to mount the ballasts in the same spot, and for good measure, I screwed them into the headlights. Then I mounted the ignitors to the side of the headlights too using 3M tape.
I riveted the relay to the side of the engine bay, and I mounted the box for the anti-flicker module on the side of the fuse box, as seen below.
Here is a before and after. A close up pic isn't ideal to show the difference because the HID bulb will have more penetration through the darkness than the halogen, but it is all I got. The halogen bulb was a Sylvania Silverstar Ultras, which was suppose to be "white", but was clearly yellow next to the boomerangs and DRLs. The HID's are much whiter.
Apparently these bulbs require some break in time before the color matures, so I'm going to give it some time and then I'll get some night shots.