Thats vibration damping material not absorption. A good carpet underlayment with sound absorbing foam, would provide additional absorbtion. Someplace on the site is pic of someone that used good absorption material on the engine cowl in place of the OEM fuzzy crap.
SOundproof Cow is a good source of info and material if you want to go a step further.
You did a great job on applying the damping.
2005 Bigfoot 1500C8.2 Truck Camper; MANY mods, to many to list
2007 Chevy 2500 Duramax Std Bed Ext Cab