I believe they are labeled off road because of the decibels. I ran them with the stock H pipe and stock headers/cats. I'm not sure what Roush did out of the factory, but these were not an option. I believe these were included with 427R package, but you had to install them after the purchase. I know I would scare the crap out of people when I stomped on the gas and would easily setoff car alarms. I purchased my car used with 22k miles on it...don't know how long they were on the car so I can't help with a possible break in period where they could get louder.
2007 Mustang GT/CS Convertible - AT - Redfire
Bama 91R-V2 Tune - Roush CAI - FRPP GTA Axlebacks - 3.31 Gears