If your O2 sensor is only after the 1 cat then yes as long as the O2 sensor is after a cat. if it is after both cats then, well, I just don't know if you will trip any codes. Usually the second cat is just far enough away to make it difficult to relocate the O2 sensor due to wire length. If you were going to remove 1 I would remove the second or the one closest to the exhaust tip. I do know that you can buy universal cats a little longer to make up for a 2 cat setup. The standard seems to be 12" on universals and some offer 18" cats that would probably be the way to go if your sensor is after both.