When installing HID lights in a 2001 or 2002 Toyota 4Runner (Bi-Xenon H4 HID Kit), you need to disable the Daytime Running Lights. This is because the DRL circuit lowers the voltage to the stock halogen light bulb in order to create the DRL effect.
When installing an HID bulb kit, if your truck sends the 6v signal to the headlights for DRL, it will upset the new HID ballast and the xenon bulb will flicker like a strobe light.
The fix for this is to disable the DRL circuit. The following write-up will show you how to disable it temporarily with a switch. If you are installing HID lights and do not plan to ever take them out of the truck, then the switch is unnecessary. Simply disable the circuit and forgo the switch installation.