Aqua Power Ltd makes the same design as the old HPIs except they are quieter, flow better and made better. If you are running in salt water be sure you get mufflers made from 316 sst not 304 sst. Also a muffler will reduce noise levels by a certain number of dbs (depending on water flow) so unless you know how loud (in dbs) it is open system, nobody can tell you what it will be with their mufflers installed.

Gibson bullet got it down to 88