Oh, a stebro that rusted?? That's odd- it should be stainless...
to be accurate, i said "rusty" as opposed to rusted out. not all
stainlesses are completely stainless.
304 is good. 409 rusts. 304 is more expensive (and probably harder to
work).
I think that one reason stebro is so reasonably priced is that they use an
inexpensive alloy. fwiw, the exhaust tip is not rusty - maybe because of
the oil/soot all over it.
The system has lasted quite a while, its just not a pretty sight (although
certainly no worse looking than a regular mild steel system).