CORSA Performance Xtreme Valved Cat-Back Exhaust The CORSA Performance 21317CF is an Xtreme Valved 3.0-inch cat-back exhaust for the Cadillac CT4-V Blackwing. This system features 4.5-inch carbon-fiber twin tips and a polished finish. Designed for the 3.6L Twin Turbo V6 with the factory Active Valve