If you take the carpet out you will see this black tar like stuff on the floor of your car. You can use a air hammer with a chisel bit. Just be carefull not to put holes in the floor.It takes no time at all if you use one.
The sound deadening, pad under carpet and the thich pad on the firewall in the car all = 50lbs.
The back seat doesnt realy weight anything and just makes the car look gutted when removed.
I would remove everything in the hatch and keep the rear seat and hatch cover. Manual widows also dont realy save any weight in dsm`s. Just under a pound per window.
Wheels and tires are a good way to loose a good amount of weight.
A set of 16" rotas and Toyo`s an save you a good 60-70lbs from stock wheels and tires. Toyo proxes are one of the lightest radial tire you can buy.
Corbeau FX1seats weight 16lbs each compared to the stock front seats which weigh about 90-100lbs for the pair. Thats about 55-60-lbs saved their with race fixed seat brackets.
You can also get a carbon hood and save some more there.
You can loose a good amout of weight with out making your car look like the typical gutted honduh if you do it right.