Are you running stock bodywork? Eh, nevermind. Good luck! Trying to make that thing not sound like a trashcan, I would think you'd have to reduce its volume by hacking it to shape or backfilling where you don't want flow, and matching up to existing aesthetic lines... It looks to me like you could get a decent internal shape, kinda like a regular, but bent and twisted slip-on, by sealing off areas with some sheet metal. Your perforated pipe, I would make a cone from the inlet to the outlet, with the cone encompassing both the small and large outlets. May even be able to shape a reverse cone prior to reaching the outlets. I'm starting to like the idea.
