Sorry it took me so long to post back, guys. I've been really busy lately. Some of you are saying that on your 2003 your lows stay on when the highs are turned on. That's probably the case, since reflector HID was an option for the 2003+ models. I can tell you that's not the case with the 2000-2002 models though. Here's a diagram I created for the harness I built.
The diode is there to keep the low beams on when the high beams are switched on. The capacitor is there because when the high beams are triggered, there is a very small amount of time where there's no power to either high or low beam stock plugs. So, what would end up happening is that the power would be cut to the ballasts for about 400-500 ms while the highs turned on, and then they'd both have power again. That very quick re-strike is just as damaging to the HID bulb as what we're trying to avoid in the first place. So, I've put the 4700 uF capacitor across the low beam relay coil, so that during that intermittent power drop, the low beam relay stays closed and continues to draw power from the battery.
I'm not sure how you have your HID kit hooked up, but you really shouldn't be pulling the power from the stock harness. This is a big no-no, and especially with cheaper ballasts like this kit probably has. These cheaper ballasts usually draw a lot more juice at start-up than an OEM ballast. The harness is really easy to build, and you can build it for right around $30 parts.
If you don't want to build a custom harness, then you could use the ideas (diode from high to low ground wires, and capacitor across positive and ground low beam wires) from the harness I've posted and modify the stock wiring. I don't see why that wouldn't work, but it's best not to go cutting up the stock wiring; it's all up to you.
A little info on my HID setup:
- Lexus LS430 Projectors retrofitted into the stock 2002 headlights
- Denso Slim Ballasts (from the same Lexus LS430 the projectors came out of)
- Brand new Philips 85122+ 4200K bulbs
- Custom wire harness