The two engines are mostly the same, but the FFV has flex fuel capabilities (can run on fuel that is up to 85% ethanol) while the FI can only run on normal pump gas. Easy way to find out would be to look on the back of the car, the flex fuel cars have a little badge that says flex fuel on it. If you want to be absolutely sure, you can check the VIN on many free websites. The VIN is a 17 character string of letters and numbers. Easiest way to find it is to look from the outside of the car, check near the bottom of the windshield on the driver side, or on a sticker on the driver's side door jamb.
Most parts are the same between the two engines, but it's worth it to know which one yours is for the few parts that are not the same.
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