hi, guys, need a bit of help with a 53 plate tdci focus i replaced the fuel filter & took the car for a run .shortly after joining the motorway, as i went from 4th to 5th gear there was a slight bang, the car lost power. it would not go over 2000 rpm,even if i floor the pedal. i struggled to the next exit at about 45mph . there are no fuel leaks & the pipes connections on the filter are ok . ( i was thinking it may be a air leak ?) the throttle pedal feels " soft " any ideas ? cheers, steve.