I have a 2013 Challenger SXT and I want to get a CAI for it. Should I go with the Mopar or the K&N? I also want to remove the exhaust resignators and replace them with some Flowmaster 40`s. Does anyone know how much this would cost me? How much horsepower and MPG woukd I gain? Would it sound like a R/T? Would it be worth the cost?