Quick question for anyone who might know: Are the OEM downpipes fitted on 1st gen. 4runners with 22re motors made from stainless?

I know for sure the manifolds are cast iron, and the tailpipe/muffler/midpipes are galvanized/zinc'd. Not sure about the OEM catalytic, but the downpipe itself, I am truly stumped.

I am using a factory downpipe in my build of an oversized exhaust system from the manifold back, and during the welding stage where I used the 2-1 segment from the downpipe, it welded like a**. I'm using oxy/acet and I'm having no problem welding other parts of this system. I'm cleaning the galv./zinc coating off before welding, and yes my settings are correct. The material from the downpipe is just something else, and I'm feeling like it's stainless, can't can't confirm.

Anyone have an idea?

-Chris