I had my Cobra's pipes made with Lobak sprint car mufflers.
They have approximately a 4.5" body with 3.5" inlet/outlet, and use a straight thru center tube with spiral augers around the outside. There's no packing material whatsoever, so they stay consistant over time.
With the 12.5:1 427, it's fairly loud, but has a very crisp, pleasing sound.
I just use common sense and ease up on the throttle when passing a cop.
The only attention I've ever attracted from police was to look at and talk about the car.
I run an open header with a turndown on the race car and always use earplugs. It would be downright painful without them.
Later,