Replaced the stock JBL sub with a High Power Poineer bad vibrations now ..any cure???

It was horrible whan i first finished because I put the plastic covers back on....bad idea they almost killed the entire sound becasue of vibrations. So this afternoon I pulled the plastic covers out from behind the seat and the sound quality jumped 1000%! but there was still a lot of vibration now brings me to my next problem .... Since the speaker box is bolted to the back wall of the truck it causes a lot of vibration where the bolts attach it to the truck how or what should I use to prevent this? I stuffed a clean shop rag real tight in between the box and where it was vibrating the worst and it really almost killed the whole problem but I am looking for something more sano and permanent .....anyone have a fix for this??

It's killing the quality of the bass and sounds horrible from the outside of the truck!

Yes I am running an separate kenwood amp for the sub now and still using the stock one for the door speakers

 

have you tried putting a little silicone between the bolts and the wall that might help dampen the vibrations, thats what my friend and i did to his car.