I have the exact same problem. I have a 95 corolla.........Corolla's are HORRIBLE for rattling. What I had to do was take out my seat, and jam sponge into every cresent where 2 or more pieces come together. This way, the sponge will stop any unnecessary rubbing together. I also had to jam something in under my tail light case to stop the rattling. Also, in my trunk on the left side behind the carpet, there is a vent in my car. In that vent, there are about 20+ fins in it. That was the key source to my problems. All I did was put a piece of black tape on each fin and it solved all my problems......hope this helps
put some edead v1se on the roof and floor of the trunk. for the hard to reach places use the edead v3.
but before you buy all that stuff to deaden your car, listen to the rattle carefully to see where it is coming from. alot of times you can tighten things up to reduce the rattle.
My car does the same thing guys I know exactly what you mean. You need to take those rear 6x9's (or whatever size) out, and put some dynamat around the edges of the mounting hole, then screw the speakers into the dynamat.
The best way to pinpoint the rattling is to bump ur system and go back and actually hold various parts of your car in place and see what pieces are causing the rattling. If you put pressure on a piece and the rattling gets quieter, dynamat that b!tch! LOL
Also, expanding foam works very well in those hard to access places, just get a long straw attachment and pump your car full of it! It becomes very hard and dries fast though, so make sure you don't spray it anywhere visible, because it can be a pain to remove.
i like the sponge idea, i have some socks i bought that were too big, im gonna take off the back panel and eDead it and put some socks inbetween everything back there.