15644 Magnaflow Exhaust Systems fits 19992004 Ford Mustang. 15644 Magnaflow Exhaust Systems Features Magnaflow Exhaust Systems unleash instant horsepower and torque gains. Carefully custom engineered for your specific year, make and model. Frees your ride from the powerrobbing restrictions of a stock exhaust. Built with the finest fastflowing, restrictionfree 409 stainless steel tubing for a lifetime of dependable duty. Reduces engine heat, relieves backpressure and improves exhaust scavenging for extra power and greater efficiency. Magnaflow Cat Back Exhaust 840 Reviews, Sound Clips & Video Install Guides for Magnaflow XL & Pro Exhaust Systems. Magnaflow 15644.