Take it from me......this car will never be light enough to be competitive on the higher levels. I just went thru all of the stuff you are talking about (trying to make it lighter) and on top of COMPLETELY gutting the car, lighter wheels, brakes, etc, etc, you would need a CF hatch, lexan windows, remove all inner door skins and frame work, remove the dash, and the list goes one. Unfortunately, this car, no matter what you do to it, will never be light enough to be a true contender on a road course at a high level. Fine for AX or hpde or something like that, but nothing on a high level.
Do what I'm doing, build a new, dedicated track car if you want to compete on the higher levels. I just started the process of building mine last month.