On my dad's 2000 Ram 3500 6spd when cruising down the road all of the sudden it is like the throttle drops off and comes back on, if it wasn't for the jerk of it coming back up you wouldn't notice that it dropped off.
At first I thought it was something with the cruise control but I've noticed it without it on, never had had it while accelerating though.
I couldn't find anything that exactly sounded like this when I searched through the forums.

 

Do the three key on trick and read codes at odometer. The logical things are APPS failure which almost allways generates fault codes. The other issue is a vp44 failure. There are lots of other possibilities also. Keep driving and don't take trips with unit. It will get worse in all probability.

 

And after the 3 key trick, nothing. There were no codes on it however if it is like my 04 then after so many successful key starts it resets so it may have set some and by the time I got to look at it they were reset.

 

my 99 did things like that everone thought it was the pump. buddy put a scanner on it and road around. missing 5 volt at boost senser. boost sners was bad . only 85 buck VS a 2200 pump. do some trouble shooting .