6.0L Minor Surging/ Odd Idle Troubles

[k.thed]

I've got a 2004 F350 CC short bed SRW Lariat 4x4. 6.0L/auto, 75k miles. I noticed on a 600 mile trip the other day that while traveling at highway speed (70-75 mph) with the cruise set, it has the slightest little surge. Almost unnoticeable unless you're on a super smooth stretch of road. Then after driving down the highway for a distance, it wants to idle weird. Nothing super noticeable, but a slight irratic/hiccupy idle. The tach doesn't jump around when it's doing these things, it doesn't lope, miss, or surge. There are no lights on in the dash, nothing. I can drive it around town for awhile and it never misses a beat. But road travel brings these demons out. Talked to a Ford tech and he immediately said I've got an injector 'stumbling', but I have a hard time believing that because I can put the pedal down and it runs like a scalded dog and doesn't miss at all. He asked me how it starts in cold weather, and it does like any other 6.0L I've ever been around. Kind of cranky and clatters for about 3-4 secs, then it clears right up and idles smooth as can be. Any ideas what might be the issue? I hate to think it's a $650 injector replacement that needs to be done, rather than something small. I even considered that I might have gotten a bad batch of fuel, but I've run 4 tanks of fuel and fuel treatment through it and it still continues to do the same thing. Any help would be greatly appreciated--