[Drivesthebeast]

I used dynamat in my 85 Mazda GLC...made a huge difference...but it was time consuming to install, and was a bit pricey, but that, combined with some speaker fiberfill (the white stuff) filling the quarter panels and inside the hatch, it reduced my noise a lot...it made my stereo louder, and sound cleaner. In some areas, I used rubberized undercoating and rocker guard too...that seemed to help cut down on road noise and vibration. I used tar-backed insulation and rubberized undercoating on the floorboards too.

I wonder if any of this stuff could work for you?