If some of Aqua Powers marine exhaust pieces look just like Gibson product, could it be maybe they build something for Gibson? I don't know. I don't think Gibson is building for them?

Best Regards,
Ray @ Raylar

Those Aqua Powers probably are the old HPI's. That would make sense, since both are from Ohio. I have a pair of the 4" clamp-ons which knocked down the decibels nicely, without any loss in speed. Hot Boat magazine did a test years ago with around 20 mufflers, only one or two didn't rob power. The HPI's I have are extremely well made using a high quality 316 stainless while I believe the Gibson uses a cheaper 304 stainless, similar in appearance, but not the same.
Steve