Hey anybody ever notice a weird vibration or engine lope when you are in traffic say at a stop light and you let off the brake to barely move forward when the traffic inches up. This happens whether I am on the brake just barely or not on it at all. As soon as I give it a touch more throttle it stops. Anybody have any ideas or is it something to do with low vacuum and just letting it idle up a slight incline?

 

I have also noticed this with my '99 4wd 5.9L. I think it has something to do with a misfire or rough idle because it mostly went away when I fixed the misfire, but I can still feel it a little bit. Anyone know what's going on?