2006 Suburban Questions

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I am looking at buying a very loaded with nice low mileage ( 78,000 miles ) 2006 Burb with the 5.3 and 4L60E trans with3:42 gears and G80 factory posi. I decoded the options and it has 2 things I am not familiar with. The first is Code G69 and its called Auto Level Control, is this some kind of hydraulic or air bag system for keeping the suspension level under load. Has anyone had any problems with this set up? The other option is Code Z55 which says "Chassis Package Bi State Real Time Damping Chassis " and I don't have clue what this is. Lastly does anyone have one of these Burbs that you have put 150/175,000 miles on and if so how has it stood up. I am familiar with Burbs and have been driving them for 10 years now but all I've owned is a couple Squares and the 94 K1500 I have been driving since 2010. The seller wants lots of money for this Burb so I want to certain I will be able to drive it for 10 years without and major issues.

Did a little digging and found what Z55 Code is:

Autoride: indicated by the RPO code Z55. This suspension system uses electronic shocks in the front that automatically adjusts to road conditions, becoming stiffer or softer as necessary. The rear will use an electronically controlled self leveling air shock that is monitored by ride height sensors and inflated remotely from an on-board air compressor.