I think it's improper installation. I only know about the eibach springs. If the installer seats the end of the spring right up against the stop, you will get noises, and maybe over time it will go away. Eibach instructions say to seat the end of the spring, then back it off 1/4 or 1/2 inch (I forget exactly). The point is not to introduce metal to metal. I had small noises and squeaks I'd notice in my parking garage at work and going SLOWLY over the speed bumps in the garage, and turning at slow speed. I jhad to listen for it. That's all gone now, some 8K miles later. I did not watch the installer, but he didn't read the intructions and just jammed the springs against the stops.