These trucks don't really have a problem with purging air after you initially install fuel injectors. If you do, then you have a problem with injector o-rings or something like that. If it is having to re-prime fuel every time you start cold, it would probably be leaking fuel out on the ground constantly.
Basically, what I am saying is that it is probably not a purging problem. More likely a problem with worn-out fuel injectors.
What is your year/mileage?
Oh, and to both of you, welcome to the ORG. By the way, you might want to stop by the "User Control Panel" and fill out your signature, so people can more easily give suggestions based on your model year/configuration.