Originally Posted by StonemanQA
Was your cruise control on? I have heard it regulates speed with adjusting boost over throttle position. Boost will fluctuate with wind and slight grade changes. Mine will do this more doing regen or a stiff head wind.
like said above, the first question is, did you have the cruise on?
If so, this is the "turbo surge" many of people have noticed. It is common on the 6.4s and 6.7s
It was explained to me as the pcm trying to match torque to the speed, when the cruise control is on. (therefore increasing and decreasing turbo boost) My 6.7 did this every once in awhile and drove me crazy. if you kick off the cruise control it should stop, drive a few miles and set the cruise again. this worked for mine.
Although i tuned with H&S at 8,000 miles and my truck hasnt had the turbo surge even once since then.