I know our cars like to squat once you add any weight in the rear seat or the trunk. After I installed my KYBs it didn't lift much, but after a few hundred miles it began to. But I wish I did install the stiffer springs that Blackarrow sent me that gmpartsdirect.com carries for around $100 a set. I may plan on changing them out sometime when I get ambitious again, but not necessary mod right now. I also got a nice combo Impact wrench kit, made it soo much easier. I got an air one but wish I got an electric one so it can be more portable. Good luck, and I don't have any advice on the lower springs, sorry.