Like everyone says, please avoid HIDs.
Make sure that your wiring is intact; and that lights don't dim while using A/C etc.
Make sure that the reflector housing is in good shape, use good quality Koito 55-60 watt bulbs. If at any point you were using 90/100 watt, then your reflector housing is almost definitely toast.
You may also read this thread (post no. 2 and 10)
and this thread (post no. 12)