I need to start a "what are you attempting to do to your Mark VIII" thread.
I still have an issue about every 30th time I turn on the headlights and it knocking out the SCIL. I have aftermarket 35w HID installed, wired directly to the existing wiring. I have to pull the negative cable and re-attach it a couple of times to reset it.
I was going to build my own battery powered relay harness, but to do it right I would have a ton of money into it, or to do it cheap I don't think I would like the results.
I bought this off eBay, it isn't a large gauge wire feeding it, but all the connections look good, it has the resistors to shut off the check headlamps message, and with all the connectors (the 9006 male and female, the one for the relay) the inline fuse, and the resistors I don't think I could build it for the 11 bucks I paid. The resistors are 2.70 a piece from Hong Kong (as I have them already, but to use as a load for projects, not specifically for this), and even a couple of bucks a piece for each connector and 3-5 for the relay.
So if I ever get to installing new bumper and header panel, rip out the OEM ballast and find some good place on metal to mount the resistors, and clean up the wiring and how it runs, get this installed. I was hoping there would be a good place to attach the feed for the relay in the high amp box, but doesn't look like it.