Hmmm...

Ideally, you would run open exhaust with optimized length collectors. Generally speaking, the less restrictive the system, the better.

Sometimes Low-end torque is slightly improved by a more restrictive system. There are systems I have read about the purportedly produce more power with X-Pipes and optimized, tuned mufflers, etc.

Still, less restrictive is typically the better way to go.

I own a '79 Jeep CJ5 with AMC 304 V8. I run 3-inch pipes and Dynomax Mufflers on it. It's not quiet, but not overly loud either.

I also own a '71 Charger. When I upgraded from 2 1/2-inch to 3 1/2-inch exhaust on the 440 in it, 1/4-mile ET performance improved by 7/10-second.