Rep Power: 244

I was trying to eliminate most of my rattle from my car today (2005 civic si, candian non-hatchback)..and I noticed that when I pushed against the center of the rear bumper (towards the car), a significant amount of rattle was gone. Does anyone know how I could permanently eliminate this rattle??

Also, does anyone know how to get to the air vent in the trunk that makes the flapping sound? I read about it in other threads but couldn't figure out how to get to it.

I have:
2 Kaption Audio SPL-1200 Subwoofers (installed pointing to the inside of the car)
1 Phoenix Gold Xenon 1200.1 Amplifier
1 Phoenix Gold 1 Farad Capacitor
Pioneer Premeire series DEH-P8MP Head Unit

Thanks!

 
Rep Power: 786

The air vent is on the driver's side. You can access it from the outside from underneath the bumper, just behind the wheel well. I fixed my vent with some duct tape.

 
Rep Power: 279

Ehh i put a couple screws and some jb weld on my vent.

 
Rep Power: 244

Thanks a lot guys. Now if anyone knows what I can do about the rear bumper, please help!! By the way, I do have Extreme Dynamat on the trunk lid, down where the spare tire is, behind the plastic piece where the latch is, and behind the liscence plate. I also have tape wrapped around the latch on the trunk (it helped) and adjusted the rubber pads on the trunk lid. Thanks.

Hey guys, I looked all over for that air vent, I could hear the sound but I don't know how to get to it...I saw a flappy cover on the outside of the car at the bottom near the rear wheel well...but when I held it, somethin still flapped...thats obviously not the vent....does anyone have pictures or anything that can help me find it? Thanks.