I've had these on 2 Impalas (8th and 9th gen) on 4 different struts (factory 9th gen, Monroes on each and AGX) and they work fine . They raise the rear end to a new ride height and can handle loads much better than stock springs, but still ride well. You have to be very careful with the springs on these cars, otherwise the ride will be bumpy. They reinforce the rear end very little, so they don't affect NVH from the front or rear. It is strongly recommended to tighten the "boosting" springs. I…