Sound deadening is awesome but it can hide any rust building underneath and be a pain in the butt to get off when you realize something is hiding underneath. I bet it made driving the car much much nicer though.
I just finished my s14 with 80mil killmat and 120mil closedcell foam on floor boards on top of killmat and omg what a diff it’s night and day. Inside the car you can just barely hear the hks catback.