Could be because it is 2 1/2" tubing. The "mufflers" have some gussets supporting the tubes in and out that are not on the smaller ones. I think construction of the muffler is different, too. Mine has perforated tubes inside the tips and I can see a plate with holes in it across the inside of the muffler. Do you have the big headers to go with the 2 1/2" pipes? My headers need a dent in the gas tank and shield to clear one of the header tubes. It tried to melt a hole in the aluminum shield.
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