I had a similar question as I had read in one of the myriad articles that Dodge tweaked the exhaust system to get the best performance/sound from it but I know stock systems are fairly more restrictive than aftermarket. I saw on the Mopar Accessories site a cat back system for the Challenger but it actually looked like it had more muffler/resonator than what is under the Challenger now, anybody have an idea about this? I plan to put the cold air pack on it from the dealer before I pick it up with the 92 mm Throttle body as well and was wondering if going with the cat back system also would help with more ponies/torque. Later down the road a supercharger is slated to go on top and I am sure a better exhaust will be needed so I would like to get it now if is a bigger help to the breathing then the original one.