When I start my car or it idles at low rpm, a chatter comes from my engine. If I give it any gas, it will go away for a while, then come back at low rpms when idling. It sounds like a heat sheild, but I ripped it off and it still makes the noise. It sounds like metal pieces rattling against each other (not loud, but annoying). I opened the hood and sounds like it's coming from around the headers (I have aftermarket dc header). Any of you have the same problem, have a suggestion of what it can be? Is there a heatshield before the cat I don't know about? Like I said, it is only when I'm idling when I hear it. Any help/ suggestions would be appreciated.