if i'm remembering right, the stock oem itr exhaust system has the 17" cat converter, and two (2) resonators in the b-pipe, and finally a low restriction, yet quiet muffler.

with your setup, you are basically running no cat and - from what i gather - no resonator in your b-pipe.

sounds like the test pipe is the main culpit. i am running a spoon system (full) with a jdm itr cat. a friend is running something very similar but with a spoon cat-jack (basically a test-pipe) and his car is MUCH louder than mine; complete with the gurggles and farts. :P

if you don't run a cat, then perhaps adding a resonator will help - but probably not much.

kepani