You can purchase simulators. I did this when I took the cats out of my C5 LS1. I think the logic is that the computer needs to see a signal that is different between the two O2 sensing points so these simulators send a bogus constant varing signal that is within the limits of the computer program. They worked great for me. You can probably get them on Ecklers or Mid-America...I think they are only $40. Worth a try.
These simulators are only for the rear sensors. Leave the front ones alone. When you take the cats out, they plug into the now empty sensor plugs.