Injector cleaner isn't going to help with sticky injectors. Not on a 6.0L. The injectors on a 6.0L are fired by high pressure oil. The problem occurs on the oil side, not on the fuel side. There are a couple of products (REV-X is currently the most popular), that might help on the oil side. Another thing that might help is to use 5W-40 Synthetic oil, like Rotella T-6. It flows easier cold and lets the injectors work better.

Most off the shelf injector cleaners are not designed for diesels and can contain alcohol, which can do more harm than good.