my mufflers are rusting out and having holes in them causing my car to be louder, I use to like the loudness now not so much, and was wondering if by putting the mufflers from a gt on my gxp if it will quiet it down or if thats even possible. also is there something I could do to increase my gas mileage it's not doing so good and I don't beat on my car a lot and I drive 14 miles one way to work everyday.. don't get why the mileage sucks, unless it's from the hole in muffler and the fact my back tires are directional and the front aren't? could that have an affect on anything other then the fact the back ones hum