About the Stainless Steel meterial -> Is that the same as SUS304?
SS coated = SS ?
What about the uppipe? Shouldnt i change that as well with one without a CAT?

Is there a word for each section of the downpipe (or any other pipe in the exhaust sys) to be weldged for 'optimal flow'? I m basing my question on the fact that the downpipe not made out of just one pipe but sections weldged together.
Like Mandrel Bent for example is a word for Bending to acheive optimal flow.

and what is the difference between straight out and angle out performace, quality and noise wise?

would titanium make any difference form SS?