What material are the exhausts on the 986 Boxster?
 

I have just been told my exhaust has a small hole in it. (Failed the MOT!) I could probably get it repaired by welding a small patch on it - nothing too serious. Does anyone know what material the exhaust is? The position of the hole is just before the join where the exhaust goes from 2 parts to one. Its on the part that has the two tubes joining to one.

Any help form anyone out there would be appreciated.
Thanks