My wife picked up a mustang 5.0 and super fords magazine the other day and it had an article in it regarding the jba headers for the 6 and single muffler. They did a dyno run after installing both and it resulted in a 17hp and either 12 or 16 ft/lb of torque in the middle rpm range. Not sure how much was muffler and how much was headers but I thought my fellow v6's may like to know actuall numbers acheived. There was also a write up of how easy they were to install. It was also done on an auto tranny 6 not a manual and the install was conducted and dyno'd by PHP. If you have any questions and I have some time I may photo copy the article for everyones reference.