Just acquired a new to me 2016 Yukon XL SLE with 139,000 miles. First thing I noticed was the harshness of the ride. My first thought is worn out shocks and struts so I began looking for replacement parts but I am thoroughly confused by all the different suspension options GM has. My RPO code is Z85 (Chassis Package Increased Capacity). I looked at the rear shocks and while there is no air bag, there is a small black hose/wire connected to the shock which makes me think this is air ride. Could someone smarter than me shed some light on this?