For the issue of sound, I will coat everything, because the ceramic coating reduces the "ringing" effect of the metal tubing... In essence, when you hit a piece of piping that's not coated, it sounds like a bell.. when it's coated it just gives out a "thud" ... no resonance and therefore less noise.. it really worked well on my 944 turbo.. full 3" system, no cat and still passed noise at Laguna..

It's great when you solve your own problems...

 

Yeah, unfortunately I still have a lot of stock stuff. I am very happy with the way my car runs, considering. I think I still have a lot of potential. Piping and IC's will likely be my next mods that will max out my 18g's.