Well here's my progress on a performance 212 pipe. I started making a new pipe with some curved pieces pictured left, but then when I took my current exhaust off I realized the pipe was too small. The 212 exhaust port is 1" wide and so it needs 1" ID pipe. The one I've been using and the new one on be left are 1" OD and about 7/8" ID. AND my performance muffler is 1" ID.
So I looked around and found a scrap road frame and cut the 1.03" ID downtube out, then made a bunch of angled sections and came up with the one on the right. It's rough on the outside, welded with hundreds of tacks to prevent inner boogers forming, and has been ground and sanded smooth down to 320 as I went with each piece. That curve on the right along with the flange took me a good day's work, but it's worth it. The flange is the stock crap muffler flange with a washer welded to it which makes it 3/8" thick, and was ground out to 1.125" to press fit the header pipe in, and then port matched to fit the d-shape of the predator exhaust port. Lot of work but will probably give me another 3-5mph (almost 60mph).
After adding the next angle and the long straight piece I'm thinking of leaving it there, then making the option for two exhausts: one being the performance muffler, and another with a long cone from a baseball bat, which sounds AWESOME!