Joined: Oct 2005
It's for the limited slip diff so the clutch packs don't bind on slow speed turns. if you used a good shop, they would know. You'll soon know if they didn't as you'll hear what sounds like rocks grinding in the rear axle on slow turns. Not damaging, just really annoying. 4oz of friction modifier will take care of it.
On the scoop, make sure you clean the hood with rubbing alcohol to remove any wax and use the adhesion promoter (a small tube should be in the box).