I'm going to run straight pipe on mine with a 3" muffler, no cats. I'll have a flange near the muffler to change out (for long trips) with a brand new Chevy muffler I got off a new Duramax Diesel. I'll put off headers for now as I want a MLS system or equivalent first.
That rig is way nice. It's awesome to see the 1UZ race ready! I like it.