this is gonna sound weird but see if your cap on the overflow tank is venting ... the bottom of the cap should be tight but the top needs to "wiggle" so it can vent ...just an idea to try
oh sorry forgot to answer your second question.....the computer controls the injector pulse so a lose or wonky connection screws that up big time ...also you said in your vid that it goes away witch is suspect too but this is all my best guess so ..........?
mine was the big plug in frt of the fuse box ....maybe the best place to start ...check the whole main engine harness for damaged wire also ...your gonna need a wiring diagram. Somebody on here might be able to help with a pin number for #7 and #8 injectors i don't have that info
i had 2 trucks give me the same symptoms that you are saying and both had electrical probs. over by the main fuse box on top the fender. the rats nest wiring and plug may have a lose pin that causes funny ****** to happen. but idk i hope you get it figured out. i do think if you had a plugged cat you would know for shure
i haven't heard of any complaints about ride quality as far as "buckboard or duce and a half goes ..in fact quite the opposite .i had a 05 and it rode ok but my 15 is much better imo