After about 60k miles on the Konis, I noticed a similar sharp clunk from the rear passenger strut area... After removing both rear struts and and testing the rebound and compression forces on an Instron machine (tensile tester), it was apparent the struts had different force-response profiles (rebound & compression)... I contacted Koni, they sent and billed me for 2 new rear struts. After confirming the pass-side strut had a bad "foot valve", they credited me for the 2 replacement rears.... Koni provides a lifetime warranty to the original purchaser----or at least they did in 2014. Good luck.