??? regarding 02 sensors and off road mid-pipe

Yes there are still bungs, or holes, for the O2 sensors to thread into on an aftermarket midpipe. You simply transfer the O2 sensors from the factory Hpipe (don't mix them up!) into the corresponding locations on the off-road midpipe. Try not to damage them when removing or transferring them, be gentle.

The O2 sensors typically don't "foul" as quickly as you would think. It's safe to say that you can get a couple years or more out of them before they start to fail. Even then, all you would have to do is replace them - it's not a big deal.

People with off-road pipes can turn off the check engine light by running MIL Eliminators (plug-in or splice-in are the options) or an aftermarket chip programmed to deal with the rear O2 sensors.

You can order the MIL Elims from various vendors or even make your own if you
are so inclined...