I didn't find any posts that were specific about the version used. I spoke to Pypes and they said the xfm36 are 100% 409 stainless 5 piece modular design. You can also get cat delete pipes (pmm 10) for $20 a pair.
looks like they don't weld with stainless rods
you can't tell that from the rusty welds?
It fits great. I am going to Steve at powertrain dynamics for a dyno tune on Friday. I will try to take some video for sound purposes.