Nothing I would call a dead miss or total loss of any one cylinder, however pulling a hill loaded there is an rpm drop that comes and goes. Just when it seems like the truck is going to take off and pull strong, all of the sudden an rpm loss will occur. It may only last between 3 and 7 seconds and then the engine will pick back up. The light is usually not on at this point. I seem to see the light first thing in the morning and that about it for the day. When the light comes on during morning warm up I will read the codes at that point, like I said sometimes an 8-1 sometimes an 8-3. I was hoping for a wiring connection or some corrosion issue. Probably cant get that lucky.