2012 ISX 12 CM2250 - rough under throttle

[Rawze]

Something else that can be done for checking smoke at startup is to slide the exhaust manifold away from the head a bit and crank it up cold.. see if it is only one or 2 cylinders smoking (getting wet), etc. or if it is all of them. Unless it is oil getting into the intake due to turbo slobber, Most of the time it is only one of them due to valve guide seals or leaking injector when cold.

I have had to do that several time in the past with people to find smoking issues like that.