Don't know the part # off hand, but I can tell you that they are a major problem. If the car is still covered under warranty (05 should be unless you drive an ungodly amount of miles) take it in for new bulbs. The replacements are no better than what you have, but supposedly engineering is "working on it".
They still don't KNOW how to fix the problem, but they are "working on it"
May take a couple years...
The funny thing is they used this bulb in the 80'* and had nothing but trouble with it....now they must have thought that enough time had past that the problem magicaly fixed itself.
They were wrong!
I'll try to get a bulb number for you, but it may take a while for me to get it.