Ok, I have a 94 T/A that just turned 66K miles ( automatic ) and it recently developed a low RPM stumbling problem. When I 1st drive it, it seems fine. After a few min the stumbling starts. Car has no power at all and knocks, stumbles ( I don't hear any backfires ). I have to the press the gas peddle pretty hard so it can down shift and bring up the RPM's past 2000 - 2500. Once that happens, all the power seems to come back, the stumbling goes away and it seems to drive fine. Freeway driving for the most part is ok...going up hills on the side streets...not so much. While I am at a light, the car idles rough while in gear, if i put it in neutral it gets better, but not a whole lot. I noticed that my headlights flicker when the car idles rough ( ONLY WHEN IN GEAR ) and they do not flicker when in neutral. I had the codes pulled and I was told the car was not throwing any codes.. ( so i guess my car is fine and I am imagining all of this ). I was going to buy the 02 sensor and I have read that this problem that I am experiencing leans more toward that rather than the Optispark. I can pick up the 02 sensor ( BOSH ) for like $52. I keep seeing articles saying to replace both??? I see the one by the oil filter...where the hell is the other one? I have only had this car for a few weeks and its already driving me crazy. I REALLY want to keep it if I can get it fixed so I can enjoy it. Any ideas....anyone? Are BOSH O2 sensors good...seems like there is a HUGE debate between BOSH and AC DELCO.