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  1. Sound difference? Stock vs Akrapovic Slip On With Cat

    Yamaha YZF-R1 - R1M General Discussion
    Is there a noticeable sound difference between a fully stock exhaust system compared to an Akrapovic slip on, with the cats still in place? I currently have an m4 mid-pipe with the stock muffler and I'm thinking about purchasing an Akra slip on, but only if the sound is a bit louder.