RE: o2 sensor bypass
If you cut the cat out, and leave the rear O2 in, it should throwat least 1 code (for the cat not working).
I mean, by the book, unless you install a sim, pretty much anything should throw a code.
You mighttry what User2006 said, and tie the rear O2 to the frame rail. I'm guessing that what he did, and it must have worked for him.