Just did the front wheel wells only and already feel the difference, I can hear 1/2 of the noise reduced from the interior footwell. The front doors already have the same material, so most of the interior noise I can hear is from the engine behind the firewall and the windows. Now my car feels like a Mercedes lol
Just a though, is that white foam stuff water repellent? If it soaks up water, it'll get heavy and sag the liner (not to mention hard to dry). Any concerns with the external stick on material collecting water?