Vibrating Plastic??

[07CamryLE]

Hey all, I installed a 10" infinity sub (self powered enclosure) since then and even before the sub...the back plastic piece that covers the rear speakers would vibrate something awful...even for no reason!! Anyone have any fixes for that? OR is there anything important underneath that would keep me from placing foam under it? it doesnt appear to attach behind the seats...just lays there....any help is appreciated it!

Also, when you are grounding a sub....does the quality of the groun affect sound etc??? My ground is not attached very solid and don't know if it matters for sound or how i know if its bad...

THANKS ALL!

[w203]

Sound deadeners (ie Dynamat or fatmat etc).