So this may not be the solution you are looking for, but it worked for me. My insurance company allows me to have a different deductible for collision and comprehensive coverage. I set my comprehensive to $0 and my collision to $250. Every windshield I've replaced out of pocket cost between $225...
The 2001 (all I6 in US) have 3 cats. Downstream of the header are 2 pre-cats, a down pipe that turns towards the rear, and then 1 last cat before you get to the muffler and tailpipe.
The only free-flowing cats I know of are from Pacesetter (they only make the pre-cats) and Flowmaster. None...