I had the same problem 2 months ago, 95 Mystique LS, V6, 5 speed, 97000 miles.
Check engine light (for O2 sensor), rough idle and rough acceleration.
Diagnosis: Bad coil pack. No spark to one wire.
New coil pack, one O2 sensor, and had new plugs and wires installed at same time, since 100K was approaching.
Purrs again, no CELs since. I had it taken care of two days after symptoms came up. Don't wait too long.
