I had the Dynomax 17747 (2-1/4" in / out) on my 67 Coronet and promptly took them off. At part throttle under load they sounded like a glass pack. I reinstalled the Accurate 6885 mufflers I had taken off. Much better.

Brian - 1971 Dodge Challenger
"The Dodge, which was practically stock, just left the Mustang like you wouldn't believe."