Anybody at a muffler shop will tell you that a Mustang 3.8 will not sound good with a dual exhaust setup (40 series flows)...I was told that it would sound like a lawnmower. BUT, when they installed them, they were all proved wrong. I also had them put on 3" diameter slant cut tips, which give a much throatier resonance. They were all shocked...I get asked alot if my ride is a 4.6. Also keep in mind, that many muffler shop employees have never seen/worked on a dual exhaust setup for a 3.8! From my experience, hearing flowmasters in my car, and magnaflows in other V6 stangs, I would go with the 40 series flows any day of the week. Hopefully this helps.