Personally I'd source some thin sponge and rewrap all the stereo loom and any other wires you can get to with ease, Such as removing the instrument cluster and get in behind there.

From Factory plenty of wiring was sponge wrapped, which over the years crumpled away. When I used to drive mine many years ago(been laid up in my garage since 2009) i would sometime find small traces of sponge on my mats.

Also as mentioned about sound deadening. Whip of the door cards with the window up slap pads on the inner skin of the door and do the same for the rear wings behind the cards again. Recaros can squeak too, some electrical tape can stop this on the catches.