i was looking over the custom operating systems trying to figure out what matches my gm operating system my stock one is 12216125 i dont see a custom one that matches mine or maybe i havent figured it probly more like it anyone know what custom operating system matches that looking for sd 1 bar system its a 2002 8.1 avalanch need to figure this out so i can test this weekend trying to lurn the custom operating system on my stuff have a twin turbo motor coming up to do any help would be great thanks