Gentlemen: I just have to put a reply on this one-- here it goes!! I have a 2000 8780xp, as long as I owned it, it had a small reving of the engine,and that was all, no other symtoms like you said, called cummins to check it out, they checked it out by putting a computer onto it, they found nothing wrong and then updated the CPl,then as I kept usung it the tachometer would show always a different rpm constantly and the oil pressure gauge would do the same and most of the time it would read 0 and the warning beeper would be on most of the time -- some days I could have just traken a hammer and knocked it out-- called cummins again to find out whats wrong, they said they would be there friday or monday, that was 2 years ago, no one has showed up yet,finally this fall one day the motor slowed to an idle and no matter where you moved the throttle it would only idle, so called a cummins service store about 35 miles away as cummins will not let dealer that sells them have th computer to fix a problem, this was a time consuming process, anyway he thought fuel sensor switch on the fuel pump was bad, so had to go 100 miles to get, put it on-- it didnt do it-- after it started and run a little it died, this time it would not start, called him again, this time he couldnt figure out what was wrong, finally decided I needed a accumulater-- well that was 170 miles away-- so went to get that-- when he finally showed up to put it on , when he took accumultor off tiny white pieces started falling out, so he realized the fuel pump is junk,white pieces from one of two small porciline pins inside of accumulater, so I take off to sioux falls -- another 150 miles away for a fuel pump, so after 4 lost days and 4 grand lighter we finally got it to run and my brother and myself and another guy helped us put it in to make it run because he has a puller to take the gear off the old pump, I am not very impressed with cummins service or parts needless to say-- I think you may have the beginning of a big problem my friend-- hate to tell you that-- thats what happened to mine, there is a difference in the motors-- mine is electronic and you may have one that is mechanical,anyway-- Good luck to you!