I heard them on a stock system (with exception of Flowmaster axlebacks), and they sounded SoooOOO mean! Of course, the guy also took off the cats and that plays a part. It sounded sooo amazing. It was on a mustang GT for the Operation Wheels of Freedom tour. I got to sit in the car when a pro driver took me for a ride and it def. had more torque like power than my stock GT. But then again, a pro was driving. =) I still like to think I push my car to the brink sometimes. I'd like to get a sound like that that's CA legal. I like JBA the most so far. just my 2cents.