I have a '90 XR7, SC engine, with 201,000 miles on it. I put all the miles on myself. The car still runs great, no check engine light, so it appears that everything is working good. My concern is that I have NEVER replaced the oxygen sensors, almost everything else at least once, and was wondering if I should. I don't need to create a problem but change them as a maintance change. Any advice as to leave a good thing alone or be pro-active and replace them.