At least what your getting at is, I don't know about the numbers. Its about volume, velocity & heat energy. Most people have no reason to go to 3" complete. I had it & dumped it to go to 2.5" testpipes to a 3" cat back (B&B). I have a 380rwhp car. I didn't dyno back to back, but I noticed an improvement in throttle response.
Later
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the universe." -Albert Einstein
When was the last time you *really* did something with your Z to call yourself a Z enthusiast?