Could be an injector going, but there's a few things I'd check first as they are sort of common also.
1 - is the truck a long bed quad cab or short bed mega cab?
2 - Check the harmonic damper on the front of the engine. There is a rubber ring and 2 alignment marks. If the ring is damaged or the marks are more than 1/16" out of alignment, it needs to be replaced and will cause a vibration.
3 - Torque Converter.....could also be part of the issue.
4 - To check the injectors with this condition, the easier thing to do is bring it to the dealer. Hook it up to the DRBIII and do an injector kill test. IF you kill an injector and the idle changes, that injector is good. If you kill the injector and there is no change, that's your problem injector.