The American Thunder system comes with two chamber muffs. The Force II muffs are 3-chambers, and the Delta Flows is another muffler design completely with 40 series being two chamber and the 50 series being three chambers.
--nathan
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--silver_pilate
'91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods...
Tried and True 302 Being Built to Outrun You! heh heh heh...
--Texas Panhandle--
Check out my site