To be honest I was too lazy to search for this due to the fact that this is a novice question anyways!

I am wanting to know what the main reason for me to get the SS test pipe rather than the alum.

Is there a performance difference? Sound? Quality?

I have a bad cat and am going to replace it (Somehow it got punctured from the underside-one of the slats is bent in, and the performance seems to have gone down-I've also had an EGR code). The rest of the exhaust system is stock 2000 SVT. I am also concidering the MSDS w/y pipe in the near future.

Any suggestion on why one over the other?