I've had Koni/GC for several years and recently had a local shop press in new bushings, ball joints, etc. The rear now rattles like crazy over small bumps and I haven't had a chance to take pictures, but I happen to have a picture of the front, because I noticed this black collar out of place. Could someone tell me what this collar is, and possibly speculate what they might have done wrong in the rear? Thanks for the help.

 

Looks like a brake line bracket. The Koni shocks don't have brake line brackets, so often people will cut the brackets off of stock shocks and slide them onto their Konis. On the stock shock the fork will actually push up all the way and seat on that bracket. So, if the pic you posted was of a stock shock then your fork wouldn't be pushed up far enough on the shock body. With the koni's, since they don't come w/ the bracket, there's no surface for the fork to push up against, so you know the fork in in the right place when the pinch bolt is at the same level as the divot in the shock body.

 

Thanks, I appreciate the help!