MAF and o2 ?
The MAF measures the amount of air flowing into the engine. If you unplug it temporarily the car will still run. It will be running on the VE (volumetric efficiency) tables in the ECM. However without a tune, a "speed density" tune, the car will not run very well (ie. poor mileage and power). Once a "speed density" tune is established you can permanently disable or even remove the MAF. I won't get into which is better as that is a futile debate. I prefer the MAF since it adjusts to weather conditions a bit easier (for me at least).
As for the O2 sensors, you have 2 pairs. The pair after the CATs are for monitoring CAT efficiency only, they have nothing to do with the actual running of the engine. the first pair monitor the lean/rich condition of the engine when in closed loop operation. By default, you run in closed loop which uses these O2s and the ECM to add or subtract fuel to keep the car running at Stoich (~14.7 AFR). If you delete these O2s, you will be running in open loop and can run just about any AFR you'd want (like lean cruise to increase mileage). I don't want to dive to far into open loop vs closed loop but with this information, you should be able to do a little more research and determine which is right for you.
As far as power goes I don't think you'd pick up more than a couple (~5) HP by ditching both and your car would be much more tempermental requiring a LOT of tuning to get it to run right.

