anyone know what this rattle might be? Went to the dealer and they had no idea

 

It rattle at low rpms around 2500

 

I've had that same rattle for about 6 months now. It is only on cold starts and usually settles down once the warm up rpm drops down. I can also hear it slightly at partial wot too. I think it's the infamous exhaust rattle, not sure if it's a loose heat shield or broken baffle inside the exhaust. Recently was rear ended and had an adjuster look at the damage. I told him about the sound and he got under the car and noticed two rear bumper brackets that were just dangling loose with a slight rattle. Maybe it's vibrating those, i havent had the chance to get under there and see if i can tighten them up and check if that was the culprit. Im curious also though. I don't want to buy a new setup to only have the continual rattle.

 

maybe the heat shield above the muffler?