engine shaking badly

[slowpoke]

so dealer called. said it is a failed injector causing the shaking with use of jake brake.
I asked them to run the truck with rocker off and see jake rockers moving , they say that's normal sometimes because of the side drag from the intake and exhaust arm can cause them to move slightly. but they will look again once injector is in and valves are set.
so would I be able to tell if its just side drag by resting say, my finger on them or should i tear them out and replace ball and spring for detent's ? when i get it back, i'm going to pull rocker cover and make a proper video of whats going on in there.