i have a 04 wrx, and bought one JDM headlight, today the lowbeam burn out, (passenger side)what kind of light bulb should i buy to replace it or i have to buy a new kit.and if i want to install a aftermarket set do i need to take the JDM power adapter out?

What do you mead by "kit"? Are your lights HID?

You do realize that JDM lights are for RHD cars, so beam pattern is reversed and you're potentially producing lots of glare to other cars on the road.

Read the stickys about light bulb info. Also search for "Daniel Stern Lighting".

i know i have the hid bulbs from factory, just want to know how to replace them cause they just burned out.
thank you

Remove the light assembly, unscrew cover on back, unplug ground strap and ignitor, unclip the bulb, profit.

D2R, the only reflector HID bulb.

where can i get those D2R bulbs?
thank you

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2005-33,GGLD:en&q=d2r+bulbs

my passenger side low beam light come on this morning when i turn on the car. but i switched off then try to turn it on again, it will not on. so the problem is not the bulb it self. and i checked the connector, i got 12v from the car, but just the light will trun on some time, and some time it will not turn on. what should i check.

The connections, wiggle the wires to see if it comes on. Check the grounding points.

Sounds like a loose ground wire or possibly a bad ballast.