Originally Posted by kenwelch
The problem you are describing will not be corrected by replacing the O2 sensors. From your description you do not have a check engine light or codes indicating O2 faults. Changing the O2 sensors will make your wallet thinner giving you the feeling that you have fixed the problem....it's a brain tease.
Your description could be misfire on acceleration.
The spark plugs might be the cause of power loss on acceleration and during higher rpm. It could be one spark plug or more, but without diagnostic equipment you will just be experimenting with parts. There are other ignition parts that could be faulty also, so the spark plug change won't cure the problem. The voltage required to fire the spark plug on acceleration increases so this can be related to plugs, coils, coil to plug connector insulation (in old cars the plug wires). Because the spark plugs wear out and are the less expensive part they of get changed when looking for an easy cure. The BMW labor for installation on the M3 doesn't make this an easy decision (about 2 hrs. or $300 labor and about $200 parts at dealer price). If you will be changing spark plugs and have the skill / knowledge then trying spark plugs is an easier choice as a test. There are a few related spark plug threads here to review that might help you with the why and how issues also suggestions for locating spark plugs.
Ok, thank you for your suggestion man; i will replace the plugs in first. Hope this cure the problem.