Well, I replaced the O2 sensor on my e34 and VOILA! no more hesitation or rough idle From reading past posts, I was really skeptikal that this would fix my problem. It seems that usually the O2 sensor doesnt muck things up that much. I'm glad that it worked though. I'm even happier that it was only a $75 repair. It took a little time to complete it since I didnt have the best of work environments. I only a set of ramps and a graded road. Certainly not safe since the car was at an angle, but I did it any damn way. There's still a slight twitch in the motor sometimes when idling but nowhere near what it was. Now it's time to start looking at the AC and front suspension!