Fuel:air mix problem?

With all the more common Alero problems I have yet to see what I am experiencing. 2000, 3.4L,auto, sedan, approx 150K, the car has been getting very poor mileage and the first sign of anything wrong was during heavy acceleration (highway passing) as it would surge with a dramatic loss of power and occasionally at idle RPM's will fluctuate, the car has lost its pep. Eventually it gave an engine sensor light (O2 sensor bank 1 low voltage); O2 sensor good, TPS good, EGR valve good, Idle control sensor good, Mass Airflow unit good. I have also been directed towards a possible fuel pump issue or Cat converter problem, since having the engine problem light erased it has not returned but the problem still exists, other than what's already mentioned, the car never stalls but start-up is best when you let the fuel pump run for a brief moment (you can hear it from the drivers seat) before ingnition otherwise it needs to crank for awhile before it will start. Any comments greatly appreciated.

Welcome to AF. How is the fuel pump pressure, recent fuel filter?

"occasionally at idle RPM's will fluctuate"

Is the fluctuation rythmic? If so you may not be firing on all cylinders. I had a truck that burned through some spark plug wires and it would only go 55. I would check the spark plugs, wires, and distributer first.

On the more ugly side, I just had 5 rocker arm bolts that pulled out of the engine, stripping the threads in the engine. You could have 1 or 2 that are stripped. Dealership said it can happen with the 3.4L engine, claimed it is caused by a backfire or something. They retapped/threaded all 12 of the bolts in the engine.