[sperry]

I think you can get to both O2 sensors w/ a standard 22mm end-wrench. The only problem is when they're in there so damn tight you end up rounding it off trying to break it loose.

Back when my car was still stock-ish, I removed my front O2 sensor just one time... after that I cut the head shield so it could be removed w/o taking out the sensor, from then on I just left the sensor in the header and simply unplugged it in the engine bay every time I had to remove the headers. The rear O2 is similar, there's not really any reason to remove it just to take off the exhaust (though I realize the reason you're pulling it this time is because you're swapping exhausts).