Volkswagen Beetle rear end rattle

I have a 2001 Volkswagen Beetle that has a rattle in the rear of the car over both wheels. It sounds like plastic on plastic. At first I thought it was the struts which I replaced yesterday, but the rattle still continues. It sounds like it’s in the suspension system, because it only rattles when I drive over bumps. I checked the plastic boots that fit over the struts, but they feel firmly in place. Should I have replaced them as well? What should I be looking for? Thanks, greg64c

Check sway bar bushings and exhaust system hangers.