Well, sometimes you cannot tell if there is an injector falure while driving it. it may be intermittant and it may not fail at all times. slightly press on the throttle pedal to bring the rpms up to about 1200. do you hear a miss or a studder? lots of times the injector problem will show itself there.
theres not a real problem with driving the truck like that. I had 4 out on mine and it drove ok. just down on power when pulling a huge hill with a load behind it, EGTS go up too, but with you being stock, you should be ok in the egt dept.
I dont think CCT faiures can be comming from anything else but injector issues. it could be something with the Under valve cover harness thats causing those injectors to fail. the power for the injectors comes from this harness. sometimes they can become scuffed, and broken. or the clips that attach directly to the injectors can come off. but not really likely they fell off if the trucks not had any work done to it.