This post is only semi-technical I guess. I as I start to plan the interior teardown of my '70 Cuda and I find myself on the fence with this matting I bought.

1) From an investment or even show standpoint, is having sound deadening material under the carpet a bad thing? I was intending to only use it where the carpet jute is lacking and in key spots on the dash.
2) Do the deadening mats create any additional problems to the metal? Do they leave little tar patches or are they impossible to remove?

I am really on the fence here. I like the engine/road noise but I don't like the squeaks so I was going to use it sparingly for some dash contact points (plastic on metal, etc). I have seen people line their doors, firewall, floor, etc but I think I value "original" more than "quiet".