For all those wondering how far off a dual-port muffler for a MS440/460 (or the 044/046) is from the standard US muffler. Check it out. (Dual-Port muffler is standard equip. on the Austrailian MS460 Magnum) The USA OEM muffler vs. the Oz Dual-Port. This is a Stihl OEM part, not the NWP aftermarket unit. The difference in the side ports alone is massive. While the USA muffler isn't very restrictive inside, the Oz muffler is even less so with no deflector at all.