Since I bought the Z, I've been trying to track down a rattle in the hatch. I checked everything trying to find it. Hatch shocks, suspension, spare tire area, plastic covers, etc... For me it was the actual spring units that pop the trunk. I've seen posts about putting spare change in them to make it pop the trunk, but I didn't see a post that said they caused a rattle. Over time, they get loose where they attach to the hatch. If you turn them until it's about to pop out, it makes it fit tighter to the hatch. This completely got rid of my rattle. I suppose you could put another rubber washer on it that's a little thicker too. Anyway, hope that helps someone because my rattle was extremely annoying where I could hear it over the pipes and music in the car.