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.