I just purchased my 2004 Focus wagon SE automatic 2.3 liter w/93,000 miles. Changed oil/filter using Mobil 1 5/20. I installed new Autolite XP103 Iridium plugs gapped to .051". I drained the auto tranny pan and installed a new gasket/filter. Was unable to get the cooler line off, was afraid I would bend it so no flush. Refilled w/Mercon V was careful not to overfill. Problem: Engine idles perfectly smooth in Neutral but in Drive with foot on brake there is a vibration. Any ideas what is going on? All vacuum hoses are in place etc.