Actually I saw a locally fabricated exhaust today that was making better power than both the AR and full Termi. They used the full system headers and fabricated a 2-1 leading to a carbon skinned canister. It's a prototype but they will be putting it into limited production. Very loud!
The point is that by using an existing set of headers, taking away the mufflers, and adding an end can, and you have an exhaust that can will create great power, be a lot lighter than stock, and sound amazing. They have a 3D laser scanner that can work out the exact dimensions of an object (like a pipe) and convert it into a computer file to enable the fabrication of copies.