[QUOTE=Hi_VoLtAgE]what benifit from ceramic muff? or would the whole exhaust be done? quicker spool?[/QUOTE]

Whole exhaust would be done for any benefits. Basically keeping as much heat in as possible.

For a race car it is viable, street car not so viable. However if you can get it done, why not :D

What gains do you get for coating the exhaust after turbo?

Faster outlet velocity I guess. I still don't understand it, but apparently this can increase the "scavenging" effect. I guess it's kinda like decreasing your exhaust size after the diff to increase velocity.