Stock Exhaust Alloy?

Hi All,

I have heard that a resonated mid pipe dramatically reduces the drone on cold start and as a result I'm looking into it; however, I don't want to spend that much money on it if i eventually do go to a full cat back exhaust.

I work with a welder that is extremely good at his craft and I think we could easily install a resonator in the midpipe ourselves at much lower cost. The issue is finding out what alloy the stock exhaust is so we understand how to weld to it.

I've seen references to 409 stainless and aluminized steel mentioned, but i don't have a concrete reference on that. if anyone knows i would be very grateful.