My F650 with with C7(basically a late model 3126, has been straight piped for a little over a year now. It is 4" from the turbo to the bottom of the stack and the stack is 5" turn out. It makes is noticabley louder, but not too loud. I have had no problems with law inforcement in Iowa, Illinois, and Missouri. It sounds real nice.
I'm all for it, do it.
Michael