The problem I am having has been around for a while, but has gotten a little more noticeable since I installed a MAC cold air intake. In stop and go traffic, you will stop and it will idle at 600 rpms, but then it will drop down to 500 and kind of shudder and then go back up and be fine. It does not do it all the time, but it is kind of annoying. Any help would be great. Thanks.

 

We need more details. Engine? Truck? The exact CAI? The more you give us the more we can help.