Sounds like exhaust leak. Another possible source would be the hoses that go to EGR pressure transducer (DPFE) from the EGR valve-to-exhaust- manifold tube.
98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both
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