The best I could come up with was 14 gauge (JRE and Bully Dog). Rod at Wildcat sells the Bully Dog and is selling it for the same price as the Jardine (16 gauge) system. I'd give Rod a call, they are kicking around making their own 4 " exhaust and are open for product design suggestions. Maybe they will consider making a 12 gauge exhaust, Rod was aware the thinner wall tubing may be a contributing factor to drone and is one of the reasons they carry the 14 gauge Bully Dog.