I fabbed them myself. I bought a bunch of 90 degree 304 SS bends and 2 lengths of SS pipe and by cutting the bends and welding it in place piece by piece, I got it pretty much exactly the way I wanted it the first time.
Here are some more pics of them. Had some probs with the welder when I was welding the flanges and the collectors on, so the welds are not quite as nice as I would have liked them to be. Luckily the engine bay is rather tight and you don't really see that any more now that the engine is in, lol.