Maybe I'll tape an interview with Jason at Mischler's BMW. So that he can clarify what he meant by "bad O2 sensor." My O2 sensor wasn't non-functioning. My O2 sensor was mal-functioning, resulting in the engine running full-rich.
In neutral, under no load, I could redline. Under load, 1st gear, redline. 2nd gear, redline. 3rd-5th gear, 65mph maximum speed.
Maybe I could re-install the bad O2 sensor... P