'06 Series 60 runs rough when cold.

Any ideas would be greatly appreciated.
I have a '05 Series 60 with EGR in a '06 Columbia. I bought it a few months ago with just over 600,000 miles on it. Had an oil analysis done on the oil that was in the truck and it came out nice and clean except for the iron was a tiny bit high (that's what Blackstone said). It runs really well and I had it turned up to 515 hp on the pedal and the cruise at a Detroit shop. I think I may an injector that isn't working right. If the truck sits for more than a day or two it starts really rough and blows white smoke for about 30 seconds. The smoke goes sway but rough running stays until the engine temp comes up a little bit. The colder outside, the worse it is. I have 12 years experience with the smaller Diesels (power strokes), I am still a Ford Senior Master Tech and ASE master but no experience with the big trucks. Once the engine is warmed up, it starts just fine but there is a slight roughness to it. It has 708,000 on it now. It only uses just under a gallon of oil in 15,000 miles. There is hardly any blow by smoke from the tube under the truck. The history I have on it is that it had a Turbo and EGR valve replaced at around 500,000 miles. Would it be a good idea to just replace all 6 injectors and cups? How difficult of a job is it for a person with my experience. Thanks again in advance for any advice.

 

I know all diesels start hard the colder it is. But it feels like one cylinder is not firing right. I have run a gallon of lucas through the fuel system and it seems to be a bit better on the cold start but that slight miss is still there. I'll run another gallon through it and see what happens. I've also been told that the Vibration dampener on the crankshaft should be replaced after 500,000 miles on these engines as that can cause a perceived rough idle.

 

I think it's more of leaking injector if anything.
And I change the fuel filters at every oil change (15,000 +or-)

 

That's what I'm leaning towards.