3" mid pipe with resonator
 

This is a local special from RES (Rotary Engine Specialists) of Auckland. They get these made up to replace the cat. The resonator keeps the noise level down, and the system is near as dammed it to a straight through pipe!
 

I was a little disappointed that the pipes were not mandrel bent, but I don't think the extra money would be justified.
 

Note the old down pipe on the left with all it's shielding, and the new HPC coated downpipe with it's much larger diameter. The new downpipe has an internal diameter of 3", but the new mid pipe has an external diameter of 3", so a little bit is lost where they meet. The cat' back (or in this case the non-cat' back) also has a 3" external diameter so fits the new mid pipe nicely.