How could you do that? Your O2's are mounted on the h-pipe. If you ran open headers, you'd run more of a risk of burning your valves than messing up your O2's since they shouldn't even be on the car. If you want to check them, warm the car up to operating temperature (as the O2's don't operate under 600*F) and check with a DMM to see if they are producing a voltage reading between 0.1V and 0.9V. You'll need to backprobe the SIG (+) snf GND (-) wires. Check out a Hayne's manual for a picture.
OIC. It doesn't say that in your sig so I didn't know. Are they stock O2's? How many miles on them? From what I hear, it's a good idea to change the O2's after 100k miles anyway. I could see how maybe you could burn up the O2's from running open headers, but I'm not sure on that.