My 320i is cuurently averaging 29.7mpg which considering I drive like a nun[ish] is appalling, the highest I have ever had was 38mpg when touring round Wales last year after they replaced the Camshaft Sensor and Airflow Sensor and reprogrammed it. Mine is an Auto, but modern auto's are not supposed to be that much worse than a manual according to BMW's official figures.
Mine also has little or no low revs power, but really gets going above 3000rpm, I hope my new 320d arriving 1st March will be alot better both in fuel consumption and low down power. The engine management light came on 3 times yesterday, but I have given up with this car - Can't wait for the new one!!