New to TDR - 3500 Ram Hesitation Question

[dwhak]

I am a brand new member to TDR so pardon me if I am posting in the wrong forum....just push me along to the right place.

I have a 2004 3500 Ram, 5.7 with 75K on it. I am the original owner and at around 68K (a year ago), I begin to notice a very subtle hesitation at highway speeds (normally around 60mph). It was so slight I thought it was a road imperfection(almost like a gentle push back). Since first noticing that it was a problem and not the road, it has became worse (it will disappear for a time, then begin again). I searched other threads to find similar problems - the truck has none of the other symptoms such as stalling or black smoke. I have noticed a RPM fluctuation but that is more recent. It has gotten progressively worse to the point I am getting a noticeable hesitation (to put it mildly) when accelerating with a now not so gentle push remaining at highway speeds. I have taken it to the dealer three times for this issue. They have been unable to isolate the problem. They tried a number of tests (sorry guys, I am not as knowledgeable as most here) but came back with zilch. At one point they told me it might be water in the diesel and to run it as empty as I dared while overdosing the fuel tank diesel with diesel additive. I live in Alaska and, according to the service manager, a small amount of water vapor was freezing in the filter or lines.
I am ready to take it back again but I want to be slightly better armed than in past trips. Has anyone out there had a similar issue?

Dave