Hey Chip,
This is the text from a post I made in June, 2006:
Ford Racing Rear Exit Headers Weight Savings:
Note: All weights were obtained using a better-quality digital bathroom scale. I assume that accuracy is probably within 1.0- 1.5lbs.
Stock Muffler: 55 lbs.
Stock Cats(Both): 29 lbs.
Stock Cast Manifolds (Both): 25 lbs.
Total stock exhaust weight: 109 lbs.
Ford Racing Rear Exit Headers/mufflers: 39 lbs. (complete)
Total weight savings: 70 lbs.
Also, note that the heaviest stock component is the muffler. In addition to its massive weight (stike one), is that it sits very high in the car (strike two), and, finally, as has been noted here, it blocks a substantial amount of airflow (strike three).
The Rear Exit Header System, by contrast, is not only much lighter, but the weight is also lower. The header tubes pass UNDER the halfshafts and then the collector mufflers are almost at the same height. There is now literally nothing behind the airbox. No more heat soak. Good-bye 70 lbs!