What is the difference between the thickness of the manifold insulators of CADILLAC CTS 3.6L LY7?

6.35mm, 12mm and 25mm manifold insulator as mentioned the ad,the main difference between these are that they increase torque down low by 10%, 13% and 15% over a broader range respectively. The 25mm manifold insulator will better improve the low-end torque by increasing runner length. However, we always recommend taking some measurements to check how much space you have under the bonnet.