American thunder sysem includes two chamber Delta Flows. The Delta's are just as good for flow and still are 2 chamber but have small baffels behind the main ones that help reduce noise. If they are not loud enough for you, consider the rest of the exaust like the H pipe and headers. Even a straight pipe after cat mustang isn't very loud. Well, it's loud all the time but a real built exaust will be quieter at idle but will be much louder at WOT.