Sorry if reviving your post or if you got your answer..
Everyone else has either changed theirs to the OBX or Magnaflow round type Catalytic converters.
There is only one Cat aka Scubba.. Then one useless second resonator/muffler before the black end..
To answer your old post on the highflow Cat some corolla n tc owners have them I think theirs are Dezod types (If wrong spelling my bad). Some report with gteat results and some report CEL coming on..
Info from the Scion TC & Toyota forums sites..
I've actually just recently bought another future mod to go with the other parts waiting to be installed lol and it is a HF Cat 2.5 C/C MAGNAFLOW UNIVERSAL 59956 Spun Metallic Cat The Gesi from vibrant was too pricey for something so small lol.. I'm doing a custom exhaust but still contemplating on the header.. Weapon R does sound nice though.. & Just waiting on last free oil change & free time to do things all at once..
Will post pics of parts before I do..
~Happy Modding!