I have a 1992 Jag for around my property. It had been running great until this yr. It seems to run great out of a heated garage but once left out in the cold it barely runs. It seems to be choking out. The coil, fuel and lines, spark plugs and pump gasket have all be changed. The carb has been cleaned and all seems to be functioning as per specs. Anyone have any suggestions of where I should look next?