The ST ultras wont need the upgrade harness. They are still 55/65watt. Just a different kelvin temp color. The current draw is the same. If you upgrade to the offroad 80/100watt. You will need the larger wire harness.
my 07 takes a 9008 (H13) and a 9145 (H10 fog) I'm using Lights made by Xtreme Vision
with a D.O.T approved 8500K rating and they are super white. The 9008's are 55/65w and the fog's are 42w. I'm sure they offer 9007's. If you want check them out. There web site is www.xtremevision.biz
Anyone have any links to some 100W bulbs for use with the heavy duty harness? 2005 ST. My crappy ebay HID system died yesterday and I should have went this route in the first place. True HID is too expensive for my taste.