I picked one up for cheap $ off of eBay about a month or so ago. I got it as a stop-gap until my Roadhouse slip-on comes in. I didn't think I'd like it that much, but for the money it had to be an improvement over stock.
It's about 1/3 the size of the water heater and weighs even less than that. I haven't dyno'd, but there is a noticable improvment in response/acceleration. The sound is pretty nice... throaty, kinda reminds me of a 'vette with glass packs. Having a Midnight, I'm not too fond of the color, but that can be fixed.
I still have the RH on order, but I've come to like the Baron. When the RH finally comes in I'll have a decision to make... [

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