>Drove down to the local AutoZone to get a replacement that matched the wattage and was surprised to only find 1 available. I ended up with the "Sylvania Basic Fog Light/Headlight Bulb D2R" it was $100, but it was still much cheaper then what my toyota dealer and a separate mechanic had estimated for me (350 & 250). I'm sure I can find better bulbs online, so if anyone has suggestions on back-ups I will appreciate it.
If one is out go ahead and change the other one. D2R bulbs are $50 on Amazon.
HID bulbs dim significantly with use. Do you notice any difference between the driver and passenger sides?
The name brand Philips D2R are on sale right now for ~$32 on Amazon.
For the price they sell it at, you can get 2 of the same quality bulbs on Amazon.
I assume you are talking about the low beams. If the housing are stock you need two D2R HID bulbs. Always replace left/right bulbs at the same time.
High beams are 9005.
http://www.modifiedlife.com/2007-subaru-wrx-sti-auto-light-bulb-size-chart/