If mine smoked like that on startup, I wouldn't be able to keep it in an attached garage like I do now. Incomplete combustion in a cold engine is what causes grey smoke like that. Might be worth fiddling with timing a bit, my only concern is what effect it would have on the egr over long term. That's the trouble with tuning, is knowing what else was changed when something like an egr, dpf, or turbo was added to a given engine. Could be different pistons, cooling jets, cam duration and timing, valve material, fuel volume and timing... list goes on and on.
We've learned the hard way at work about inadvertently changing injection timing by changing injector nozzles and opening pressure at the suggestion of the OEM. When a V-16 twin turbo diesel breaks rods and spits pieces through the side of the block it gets interesting. We lost 6 engines, I think, before someone figured out what was happening. Turns out combustion was starting BEFORE tdc, not after.. very hard on an engine.
I doubt the engines we have in our tractors are that touchy, but still...
Sean