Removing injectors from a C7 Cat is not an easy task, but with the right tools and knowledge it can be done. To begin, you'll need to disconnect the fuel lines connected to the injector and turn off the engine. Next, use a wrench or socket to loosen the two bolts that hold each injector in place on top of the cylinder head. Once these are loosened, carefully pull out each injector from its respective hole in the cylinder head. Be sure to keep track of which one goes where as they will need to go back in correctly for proper operation. Now use a rag or paper towel to clean around where each injector was located so any dirt or debris doesn't make its way into your engine when reinstalling them later on down the road. Finally, remove all four screws holding each injector's electrical harness onto its respective valve cover before removing it entirely - this will allow access for cleaning inside of those parts too!