the truck starts normally, it ticks over normally. when you start to rev the truck you can hear it missfire.i have canged all fuel filters which made no difference. I have had it plugged in and the computer says there is a problem with injector 4 on the electronic side.
Maybe swap injector 4 with another cylinder and see if the fault moves to another cylinder. Then you will know whether it is an injector problem or the electronics controlling it (or the bit of wire between).
I am not a diesel engineer so it may be prudent to wait for more contributions.