IIRC, I read somewhere some of the difference is is in the intake and exhaust due to the packaging differences in the Avenger's front wheel drive vs the Challenger's rear wheel drive. My 2012 Challenger has a 5 speed auto also. Not sure if the 5 speed auto is capable of handling more torque than the 6 speed fwd trans. Your car might be 'detuned' a bit to save the trans if the torque capability is less.
I installed a Mopar cold air intake on mine. Nor sure if it actually runs better but it sounds a lot meaner. :D
What does your exhaust look like? The Challenger has duals all the way. The mufflers actually look like old school round glass packs. The resonators out back are huge, though. I've read that 'drone' is a problem if you eliminate the resonators.
Keep me posted if you do any mods.
Dallas
BTW, here's a couple of pics of mine.
