If the engine code sticker on your valve cover begins with 9G, then your engine is the smaller displacement 2.49L. There are no 0G engine codes. 1G codes (2001) are also 2.49L but they dropped the Contour/Mystique. Early model codes beginning with 8A, 7A, etc are 2.54L.
Example: 9G-828-AA is a 1999-2000 2.49L Contour/Mystique
9G-833-AA is a 1999-2000 2.49L Contour SVT
When they actually started putting 9G engines in vehicles, I don't know.
