Weapon X Motorsports
You'll drop 12lbs of rotating mass with just the rear rotors!
http://weaponxmotorsports.myshopify.com/collections/brakes/products/racing-brake-rotor-2pc-rear-complete
Also another 4lbs with the fronts vs. the 0lb weight diff with the 2pc GM/Brembo upgrades. Plus they look great slotted...