Unless you drive a LOT with high beams (read: long periods between switching from low to high to low), you'll probably do best with replacing only the low beams with HID. They aren't like "regular" bulbs. Think of those funny street lights that take forever to turn on. They are similar in that they use a spark to produce the light instead of burning up a metal filament. They also don't like being cycled from off to on and off again.
Our Gen7 models (2008+) have the low beam always on even with the highs. But since you're working on a 2007 you will want to check to see if they do or don't. Like RwP says, using diodes or some other method to keep them on will be a good thing.
Also, I've done auto electrical for years. As RwP also recommends, so do I: consider using a relay for each pair of HID bulbs you install. It removes the added load from those amazingly skinny wires used by GM and places it on a wire of your choosing, hopefully a 12-gauge or heavier (I suggest #10). Then all the stock wire has to do is power the coil on the relay. Even if you don't change over to HID, the stock H11's would be brighter. I'm going to do the upgrade to both my lows and highs one of these weekends.
Our Gen7 models (2008+) have the low beam always on even with the highs. But since you're working on a 2007 you will want to check to see if they do or don't. Like RwP says, using diodes or some other method to keep them on will be a good thing.
Also, I've done auto electrical for years. As RwP also recommends, so do I: consider using a relay for each pair of HID bulbs you install. It removes the added load from those amazingly skinny wires used by GM and places it on a wire of your choosing, hopefully a 12-gauge or heavier (I suggest #10). Then all the stock wire has to do is power the coil on the relay. Even if you don't change over to HID, the stock H11's would be brighter. I'm going to do the upgrade to both my lows and highs one of these weekends.
