I recently bought a used 6 speed manual 2015 Challenger Hellcat and whoever had it before did a mid-muffler delete. At first I thought the car was stock but was wondering why it popped on decel so much and was so loud when I would get on the gas I couldn’t even hear the supercharger whine. Well I looked up under the car and I saw where the mufflers had been removed and two pipes had been installed. It was a nice clean job, but I was tired of the plain loudness of the car and the constant popping on deceleration that I would get. I had two bottle like mufflers that I had taken off my 2014 manual 5.7L RT Challenger sitting around so I decided to put those on the Hellcat if they would work; well low and behold they worked and I swear the car runs and sound much better! What I noticed also, besides I can really hear the supercharger whine now is that the car seems to have slightly more getty-up and go than it had before. I really think the muffler delete/straight pipes hurt performance. It must be a loss of backpressure thing?