Welcome to EM! Here are some of my recommendations...
My Mom-in-Law has a '95 Mystique Zetec Auto (likely similar to yours, except the auto and Mercury badges). I've worked on it quite a bit --
It you haven't performed a tune-up recently, these cars respond well to a good tune. Carbon build-up is usually a big problem and could effect mileage, driveability, and cause a rough idle. First, getting the mechanicals clean (if it's an issue) might be where to start. Using "Seafoam" or "AutoRX" through the brake booster line can clean out lots of gunk.
Otherwise, the usual recommendation of a feedback device, like a
Scangauge, can train you to drive more efficiently. Then, perhaps look into some aero-mods and perhaps mechanical mods.
Best FE to ya...
RH77