I have a '10 GT and have the Roush Offroad exhaust
. This is my only mod.
I took this while getting on the highway. I was more concerned about keeping it on the road than keeping the phone still.
This one is taken as I accelerated from a stoplight.
I haven't taken any video from outside the vehicle yet. But I have listened to it as my wife drove it away from the house. I could hear it a half mile away (at least) and she was just driving in the neighborhood at about 20MPH.
Romping on it with the windows down is a daily ritual. There is a bit of a drone at a tick over 2000RPM. I have the 3.73 gears.
From inside it's quiet and not much different than stock. Idle is similar to stock too. I have no regrets.