I just bought one from Mopeddivision (first time buying from them, Victor was super helpful).
Going on a stock a35 top end, e50 bottom end on my Free Spirit. Once it's built I'll chime in or post a vid of impressions, to address rpm/powerband/backpressure/db levels that I too am curious about. I got it cus I couldn't source my first expansion chamber, Proma GP, and the price was right. Opting for another Techno Boss hack and weld just seemed too logical and boring, want to give new things a chance.
There are two variants, a long header and short header. I should of went with the short header for the stock jug, but opted for the longer cus the radical aesthetics, plus the limited reviews I saw seemed in favor of the longer option.
Not to blow up the spot, but if your trying to push your cart over their generous $69 free shipping, I bought some discounted hand guards they are offering; you too can join the guard gang