I'm guessing there's more than one injector on the engine. Are they all making this noise? It seems to me there was no such noise on the opposite side of the engine. It definitely got louder as you walked around the truck. Which would seem to mean that there is indeed a problem with an injector, or part of the valve train on that side.

Personally I think the dealer is wrong. It sounds to me like a bad lifter or something. Of course listening to it over the web isn't exactly the ideal situation.

I would be just as concerned as you are, that's for sure.

I do not have any such noise.