The charge air cooler outlet has increased in diameter and the attaching configuration has changed on 2006 C/K 6.6L. GM-46091-5 is installed in place of the Intake Air Heater (IAH) and allows the system to be pressurized and tested using the existing GM-46091 Charge Air Cooler Tester. Failure to use GM-46091-5 will result in misdiagnosis of the intake and charge air cooler, and can lead to unnecessary replacement of the turbo or MAF.