I bought that too. 2 sheets to put under the front carpet /wheel wells and
a sheet near the engine. I also bought 200 sq feet or R-Blox, a dynamat
knockoff.  2 gallons of cool seal for the outer wheel wells.4coats on each
wheel. A 6X10 ft sheet of 1/2 inch thick neoprene foam rubber for the roof.
Spray undercoating/ sound deadener for the front doors. A sheet of sound
deadener 6X8 ft from a dodge caravan underlayment for the floor and
such.Did I miss anything? I bought many others too,as I used them all.
Almost nooooooo effect on noise.Sorry. Get 15 inch quiet tires that  pump
to about 35psi  and you will get the quiet  you want. Oh yeah, I put door
panels(5) all over that had 3/8 inch foam inside the trim.I still missed a
few products that I used.Just cant remember all the products I used in my
war against road sound.I lost.Just remember the truck tires that you hear
at night,whining  down the highway.you can hear them for miles and miles
and miles.Same in your sweet little vanagon.I would rather prevent that
noise than try to cover it up.Also much less work.