idea for NA's. HKS claims that the Sport is designed specifically for NA motors, claiming it uses a baffled muffler design as opposed to straight-through, like most mufflers intended for turbo cars are. That's why I asked, because I was curious if there was a difference from stock in terms of low-end. Sounds like you didn't lose any torque.
You said the sound was low, but is there resonance between 1500 and 3000 RPM?