2002 Pontiac Firebird I need help

Engine Performance problem
2002 Pontiac Firebird 6 cyl Two Wheel Drive Automatic

I have a 2002 firebird, it has always been a solid running car until recently. If I slowly accelerate the car will generally act normal, but if I try to get in it at all it starts sputtering and sounds horrible, oh it also seems to be burning much more gas than normal. I ran a diagnostic test on it and the codes were : misfire on cilinder 5, throttle body performance, and O2 sensor low voltage. I was wondering if someone could tell me the correct voltage that the wire running to the O2 sensor should have, or possibly why it says throttle body performance. I mean what could be wrong with the throttle body?