I’ve noticed on my Z when I go over imperfections on the road and on some bumps there’s a tendency for the rear suspension to bounce. It’s a little annoying, I was wondering how much of this was contributed from using KYB struts on eibach lowering springs.

is it that the KYB strut is not able to handle the rapid compression of the progressive springs in the rear of the car? 
Could it be something else? Sway bar too tight? 

 

Could be a bad shock.

@grannyknot its quite possible, but the shocks should have less than 1500miles on them; Although the use of a lowering spring on the KYB's are not recommended, and probably contribute to faster wear...