I have an 09 Tahoe XFE with a ZW7 suspension package. My rear suspension is sagging and I thought maybe somebody had lifted the front but upon inspecting the rear shocks they appear to be "Rancho" shocks. I wanted to go back to stock suspension but the GM20833776 shocks have been discontinued and the dealership told me to replace them with GM19158785 shocks. When I tried to order them from GMpartsoutlet.com it automatically cancelled my order saying those shocks weren't right for my vehicle. If I understand correctly the XFE seems to have something beyond the general ZW7 package? Any help on how to get my Tahoe sitting and riding right again would be appreciated.