Only exhaust I have seen with dyno sheet is Akrapovic and Two Brothers. Not sure how Akrpovic sounds but dyno does not show much improvement over stock IMO to be worth the price. You can look up the Two Brothers on youtube. Its called tarmac exhaust, the dyno sheet looks good but sound like my four wheeler muffler, could sound better in person but I don't care for how it sounds in the video. The TBR exhaust will not be available until January.
Would the videos of exhaust on 250's be a good example of how it would sound on the 300?