there are two sets of o2 sensors, fronts and rears. your front o2 sensors communicate with your computer and let it know your air/fuel ratio therefore adjusting the amount of fuel you use. your rears are only for emissions purposes. in other words, you must have good front o2 sensors. the rears can be removed with no problems except a check engine light, which is curable with a tuner or a set of Mil eliminators.
O2 sensors causing a choking in power? I don't think that's what he meant.
I mean, if you have bad o2 sensors, you should get a check engine light, and your air/fuel mixture will be off a tad (nothing extreme, though, not enough to choke you out at 5000 rpm, but I've been wrong before).
Your car does have four catalytic converters that can get clogged, however, and having clogged cats can hinder your performance...
The o2's do nothing at full throttle. At the full throttle the computer uses a preset(tune) setting. Meaning at full throttle the computer is not reading the o2's.
The o2's are used for part throttle driving
and you don't always gets cel with they are bad (fronts ). I had 1 go bad on the dyno and it was only seen by data logging. And I kept driving it like that for 2 months and never popped a light and never hurt full throttle performance but did hurt the mpg pretty bad