2003 deville

I am not sure what the asterisks are meant to represent, but I would assume you are describing a rough run. In some cases, misfires that are only noticeable at idle, are results of a compression related issue. The first thing to do would be identify the cylinder that is misfiring. Swap the ignition coil packs from side to side and see if that changes it. If not I would look toward possibly a cam follower that has been dislodged, and creating a combustion concern.