Mystery noise - ANY IDEA?

I recently changed the rear shocks on my 2007 Aveo5. I replaced them w/ KYB and used their boot kits and mounts. Every since then whenever you hit a bump there is a noise in the rear like soumething loose and rattling. I checked the mounting bolts and they are tight. Any ideas :confused:? Also sometimes there is a thud that feels like it is directly under the front seats when you hit a hole/bump hard. I have changed the lower control arms, inner tie rods, outer tie rods, stabilizer bar links, front struts (KYB - used the factory boots this time), wheel bearings, and recently put on new calipers and rotors. The car handles so much better now and everything feels really tight now. But I still get this strange thud sometimes. Any ideas would be appreciated!

I used new front strut mounting kits from NAPA. The KYB kits did not come with a new top washer/bracket.