In addition to the CP4:
glow plugs (yours likely have all been replaced by now or need to be)
fuel filter head leaks (nothing new to this model)
weak pistons (might want to watch out for big HP tunes)
numerous emissions systems trinkets that are failure prone (def tank for one, and not cheap)
You can search and find many threads discussing these items
Problems with early 2011 LML trucks were fixed under warranty and the injectors had a warranty extension. Hopefully you bought the truck from a private party and they provided you with this information as well as records of all maintenance and service work that was done.
There was a problem with the DEF tank heater and with my truck it was replaced by GM at no cost to me. Glow plugs are primarily a problem when the GM ones are replaced with off brand ones usually purchased on eBay. Same applies to the off brand glow plug controller.