Don't you still have stock wheels??
Change to rotoformed wheels.
Every 1 pound removed of rotational weight equals around 10 pounds of static weight, u can get the rear wheels on rotoformed wheels as low as 18 lbs apiece, just say if u get 22 pound rear wheels, savings of 14 pounds is like shaving 140 pounds of the car.
Tsw has the best priced rotoformed wheels I have found.
I am waiting for the tsw bathurst to come out next year in 19x10.5