Welcome onboard.
There's a zillion reasons for CEL (Check Engine Light) to come on, only code read can give precise reason.
Regarding EGR valve I got 19 hits using search feature, you may wish to try this: egr/problems/subject only/any date.
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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