Check out the thread titled "Injector Availability" if you are in the mood for a story.
The long and short, I was waiting roughly 6 weeks for my first injector and GM was very helpful in getting it, but unfortunately it did not resolve my issue. So, the truck is at a new dealership today and the service advisor told me that GM just received and sent out 3,000 injectors......and they have 6 of them in stock for my truck with an additional 2 coming from another local dealer. It might be worth a call to another dealer just to see if maybe they got some ahead of your dealer.