Is this an air ride system in the back 1/2 of it? If it were mine I'd find a find a truck service center and do the upper and lower ball joints , new knuckles, rag joint and Helwig bars frt. and rear. then an alignment. That alignment is not an end all bring it back in about 45 days you will be really pleased.
My mom has almost 200k on her '06 and there aint a thing wrong with the suspension. My recommendation would be to leave it alone. If you do need to fix/replace something I would put it back stock and you will likely have a better ride, mileage, and longevity.
Loc: The Great State of Texas
Leave it alone in my opinion , modified my truck's suspension , my fault went overboard / tires and springs , wish I had it back to stock now . When time to get new tires will change it all back , kept stock parts .
I went with the Rancho Quicklift system for my 08 Tahoe. The front coilovers come with RS9000XL adjustable shocks and provides a 2 in level. Added the same shocks in the rear. I'm pretty happy with it.