2012 ISX 12 CM2250 - rough under throttle

[Rawze]

it could also be valve guide seal leaking on it causing all of the grey smoke. That is a common issue of valve guide seals leaking and causing that grey-ish smoke with the newer ISX engines.

part of what your describing sounds also like maybe the egr cooler is partially restricted or not cooling the exhaust gasses enough and it is causing the turbo to get over-worked at idle. That or you have a poorly-rerading egr pressure sensor or possible clogged up Delta-p sensor or piping feeding it etc.