Not much dude! Rear seats weight less then 20 lb, air box removed??? You don’t do that for weight saving, you do that for better airflow!
Aluminum exhaust will save you some weight, proximally 10 lb depends if the exhaust has a resonator or not.
The only thing that will save you weight is the sound dampening stuff, that is about 50 lb right there.
I have the same car and I have HKS high flow cate-back exhaust, down pipe, intake, and no sound damp.
Removing the rear seats is not for every one, will get the cops attention and you will not be able to carry more then one passenger in the car…
Good luck!