Installed "new" used rear struts and now more problems?

So I scored some rear struts off a 99 STS with 75k on it, installed them on my car (99 sts with 150k) and they work perfectly. BUT Now "service suspension, service stability system and service idle control" all pop up on my DIC. They never showed up until I installed the struts, I've checked and checked all the wiring, air lines ect.. all are fine. I'm hoping it's something simple if all of these popped up at one time, but I don't have a clue where to start, I've cleaned all ground locaions, unhooked the battery to reset everything, no change. Car is running fine (besides randomly blowing etc fuse?) Only codes are : C1721, C1722, C1782, P0550, P1520. All are history, but when I clear all the codes and take a drive they all come back and still pop up history. Any ideas? thanks for your help!