2001 BMW X5 Replaced fuel pump and still has starting probl

My X5 surged 3 times, then cut out on the highway 2 weeks ago after driving for just over 1 hour. It wouldn't start after that: starter engaged, but engine would not fire. Towed 27 miles to service centre. Started after coming off tow truck. Faulted as cam position sensor. Sensor replaced, but engine cut out again on test drive. Fuel pump replaced. Car ran fine on test drive. When I went to pick it up, it would not start. Starter motor stayed on, then car almost started but ran rough and cut out when gas pedal pushed. Service centre said it was 'out of fuel' although 20 litres (5 gallons) was showing on the gage. Car ran fine for 2 days and was returned to me. It still starts badly every 3 or 4 starts, with starter motor staying engaged or re engaging, and the engine not firing. When it does start, it revs to 1800RPM, then drops back to idle. Occasionally when driving, the engine surges/looses power, but does not cut out. Ambient temps in Perth Australia have been between 80 and 100F for the last 6 weeks. Could this be the automatic choke function?