Rear Suspension Springs problems of the 2007 GMC Yukon

I have a vehicle with a ride package called premium smooth ride with a gm factory code "zw7". Both gm and gm dealerships have a catalog issue that resulted in me buying an incorrect and dangerous rear shock. I have worked for 6 months to resolve the issue and have a vehicle dangerous to drive as the replacement part referred by gm is incorrect. The oem manufacturer (sachs) in france has concurred that gm is at fault. Gm is having consumers put on a factory replacement part incorrect for vehicle and will not allow me to speak with anyone within gm to resolve the matter. I have it well documented and it has also been an issued for Yukon owners with the "premium smooth ride" option. Sachs in france provided gm with a factory shock with "nivomat" technology that shared the ride load with the rear springs. Sachs has since discontinued the product and as such no replacement part can be bought. A change of both the springs and shocks must be done and gm refuses to acknowledge the requirement or offer a solution. Instead they send drivers down the road with a dangerous ride set up. When we drove our vehicle after using the gm recommended shocks, it rode very rough and when we got up to speed it actually bounced around on the highway and was difficult to keep on the road.