Wow, that sounds an
awful lot like my current setup! I think that my intermediate pipe is like 2.75, but other than that, it's really close.
(Well, except for the DMH e-cutout 
that I added a couple months ago...) 
When I installed my headers, I needed to have an exhaust shop make the little piece that ties the Y-pipe in to the cat, & when I did, I swapped to the new muffler too - & I told 'em that I wanted the
quietest free-flowing muffler they could get.
(I already have a red car, I didn't want a whole lot of "official attention"!) I've little doubt that it flows pretty well, but
MAN, it really
IS too quiet sometimes!
