As you can see I have a 2000 model truck. Were all cars made at that time made 50-state complient by then or were there still Californian spec models? The reason I'm asking is that I'm thinking of removing the main cat. Our "Smog" tests aren't as strict as yours (at the moment) and if all cars that age passed the Californian limits, its been surgested that it might pass on just the two pre-cats over here. Last years test, she passed with a CO output 10 times cleaner than the limit here!
If I were to replace the main cat with a straight-through, what whould I have to do with the O2 sensors?

 

the califorina models have 4 cats if im thinking correct this is the only difference

 

I took my truck to a specialist exhaust maker at the weekend. Up on the ramp, we could only find one cat, the main one, just after the y-pipe. Couldn't see anything on either of the downpipes and we had a good view right up to the manifolds. Sufice to say, I won't be removing it! I was curious to see how loud it was without any muffler, as I'd heard that the cat does quite a good job of quietening the engine. B******t is what I'd say! It was way too loud to attempt a straight through system. This guy will either make you a custom system or sell you the parts to do it yourself, so I'll be getting the parts sent to work!
Hopefully I'll get some pics and possibly a sound clip done when its finished.