hes talking about the factory muffler off of a trailblazer ss.
Also, go ahead and try it, it might sound decent. However, is the STI exhaust 2.5" ID? If not you will most likely be impeding the flow of the exhaust (and losing power) by stepping it down to a smaller diameter.
why or what are you trying to achieve by adding an "STI" muffler, out of so many mufflers that are proven to work on our trucks... Do you just have one laying around for free? or are you after a certain sound??
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