My 2001 Astra 1.8 runs very rough till it warms up. The revs fluctuate till it warms up. The problem is getting worse the car now stalls the first 2-3 time I start it up from cold. Also it feels like something is pulling it back at high speeds, the car doesn't want to accelerate. The engine light is on and give out a code that its running either too rich or lean. The car runs and starts OK at idle once warm. I think the problem is either the Oxygen sensor or the Air Flow meter.