just changed fuel filter, still cuts out and doesnt start like it gets no fuel on 2001 Ford Focus

when we start it after being off for a short period of time and it idles real rough in drive or reverse. it does fine in park or neutral. what else could be wrong with it? i hooked up diagnostic tool at auto zone and it said po300

Asked by for the 2001 Ford Focus
You need to have the fuel pressure and volume tested.