Flowmaster American Thunder Cat-back Exhaust System. 2015-2019 Dodge Challenger SXT with 3.6L engine.. Flowmaster's American Thunder Cat-back exhaust system for the 2015-2019 Dodge Challenger SXT is perfect for the person looking for a moderate exterior sound level while maintaining a mild interior sound with all of the performance benefits that you would expect from Flowmaster. This bolt-on cat-back 409S stainless steel system for the 3.6L engine features 2.50-inch mandrel-bent tubing and includes a Scavenger X-pipe crossover for a unique deep sound and maximum power. The dual Super 44 Series mufflers flow into dual 2.50-inch mandrel-bent tailpipes which are finished off with tuned resonators and stainless steel tips that exit within the rear bumper valance. The exhaust system is covered by our Lifetime Limited Warranty, is designed for an easy fit and includes all necessary parts and hardware for installation.