I am sorry to resurrect this old thread. Have you figured out the culprit yet?
Sometimes inverted struts (like bilstein strut) can cause noises due to insufficient lubrication of the upper plain bearings. Google "bilstein inverted strut bearings" and you will understand which bearings I am referring to. Many Subaru sti's had this problem. Easy to fix but you have to dissassemble the whole strut. You can either refer to bilstein itself or to a Suspension specialist who builds custom made suspensions. Good luck!
Sometimes inverted struts (like bilstein strut) can cause noises due to insufficient lubrication of the upper plain bearings. Google "bilstein inverted strut bearings" and you will understand which bearings I am referring to. Many Subaru sti's had this problem. Easy to fix but you have to dissassemble the whole strut. You can either refer to bilstein itself or to a Suspension specialist who builds custom made suspensions. Good luck!