It sound like the electrical system on your truck is the cause of your problem, a Heavy Duty Headlight harness will most likely remedy your problem. You see HID's require a large amount of voltage to initially ignite the bulbs, and when the OE wiring (Which pulls the power from your headlight switch) can't provide enough power for both bulbs to ignite, only one bulb will and the other will "Flicker" or not turn on at all. A HD Headlight Harness will draw power directly from the battery, and provide the HID's with 13.8 Volts thus providing them with plenty of power. I have a HD Headlight harness in my 94' with HID's in my highs and lows, and have zero issues!