My 07 5.9 twice now in the last week upon cold start up ran really rough for awhile until warmed up. Kitty ran away prior to this problem, could this have affect on it ??? Is so why and if not any ideas as to why this could be happening all of a sudden. Other mods listed and has approx 3700 miles on it.

 

How cold was it? Did you notice the grid heaters cycling? When it's cold (like teens), and I haven't plugged it in, my '05 will run rough only until it hits the 1000RPM cold-weather-high-idle, which is about 2 seconds.