aFe MACHForce XP 3in 304 Stainless Steel Cat-Back Exhaust 16-17 Chevy Camaro SS V8-6.2LaFe MACHForce XP 3in 304 Stainless Steel Cat Back Exhaust 16 17 Chevy Camaro SS V8 6. 2L This cat back exhaust system incorporates factory style NPP dual mode exhaust valves which use the factory exhaust valve motors (not included). The valves help regulate, direct and control the flow of exhaust gases by opening, closing, or partially obstructing passageways depending on throttle position for maximum performance. Dual free flowing mufflers are used