The 06/07 has a 2.5 inch mid pipe and a 2.25 inch diff back. (i bought naulis old diff back). Some Sti mufflers had a 2.5 inch diff back section, i have the 2.5 inch version on my xt, but i'm not sure what model it's off. I was thinking maybe a JDM Sti.
I think the spec c has a stainless version of the titanium s204 cannon muffler.
Here's one for sale.
http://www.rexnet.com.au/forum/index...owtopic=120752