Replaced both my track arms today.
HOLY COW. What a difference. No more of that really loud rattling whenever I went over rough road at slow speed.
I went with the 987 track arms. Physically at least, they appear identical to the 986 arms. I shot a bunch of photos of the two side by side and posted them on my flickr site:
https://www.flickr.com/photos/billsalina/
$160 each from Pelican. Came in a TRW box but appears to be genuine Porsche with the triangle logo dremel'd off.
Ok. time for a steak and a beer!