Can someone recommend some sound deadening material?

Hey,

I was hoping that someone could possibly recommend some sound deadening material/coating that I could pick up. The reason why I ask is because I went a bit overboard on the exhaust system on my Duster and got a 3” system installed on it with the flowmaster delta 40’s. IT DRONES LIKE CRAZY!! But outside of the car is sounds SWEET! I am getting it painted this April and will be taking some parts out of the interior so I will have an opportunity to get something in there between the floor and carpet. Also, if it insulates that is great too! (I do not have a heater in it!!) I swapped that out for an electric water pump!

I will be running this right from the firewall, along the floor right back to where the rear speakers are.

Any recommendations/advice is very appreciated!!

Thanks!!!