Stainless. Get someone with a mig welder with stainless wire to weld it up. I cut open a cat box and gutted it and rewelded it with stainless with no problem. The bypass is made from the same metal. Where did it crack?
It's stainless for sure. If you can find someone that can mig weld an exhaust system, they can probably do it. Check and call around to some welding shops. Ask for a price estimate. Maybe $50 or so. If they do a really good job, give them a nice tip and remember where they are for future work.