its under the car, located where ur catalytic converter is

 

the next possibility would be the shifter heat shield (located under the car directly beneath the shifter console). it can rattle as well.

 

here's what I don't understand, why would these heat sheilds only rattle when the car accelerates? It's not like the engine isn't running when I'm not accelerating. If they are just loose metal plates then they should rattle all the time and not just during acceleration.

 

different vibration frequencies will make different things vibrate. If you have ever heard subwoofers go throught a "bass test" before, you'll feel the vibrations in different places for different frequencies. The same applies to the engine. The rotation during acceleration is at a different freq than when idling.

 

yup, all about sound waves and frequencies

 

makes sense.

 

just like sri's have slight whistles at certain rpms

 

Just pull em all off

 

would pulling all of the heat sheilds off affect anything? performance? comfort or anything at all?

 

seriously dude, check the ones on your catalytic converter. When I installed my exhaust I checked some of those out and some bolts were lose causing it to rattle. And when some bolts got stuck half way through, and I left the bolts lose to make it easier when I got back around to working on the exhaust again, it rattled SUPER loud under acceleration. Just chck them out. I honesly couldn't tell you whether it's a good idea to take them off or not. I mean, I don't think it would do anything, but then again, they did put them there in the first place so they're there for something. It's your choice really. I don't think you'd ever see any negative effects by taking them off, but you could also just find it and torque down the bolts and not worry about it.