sold my 2011 gt which i had flowmaster american thunder mufflers,this was a great sounding car with a little drone around 2000-2400 rpm,everyone could hear it coming. still had the mustang fever so when i found a 2011 v6 rousch dub edition for sale at a super price i bought it.miss the v8 sound,but , after installing the dynomax vt, it has a sound i can live with ,it will never be as deep as a v8 but i also have come to love that its quieter down the highway, with no drone,i actually cut some one inch high " L" shaped alumunum pieces 9" long to keep the flaps open all the time, the car is louder all the time, but still not real loud at highway speeds, NO DRONE, BUT WHEN YOU GET ON IT, it still has a great and louder sound that it would have with the flaps working, To rate againest the flowmaster,the vt are 1/3 as loud at highway speeds and 1/2 as loud at full throttle,but half as throuty. still not bad for a v6, i would buy again. thanks pappy