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  1. Volkswagen Passat B5 Discussion
    I have a an AUG 1.8T with a high flow CAT and APR stage 3 turbo and programing. Lately I have been getting CELs every couple of days. The ECU shows codes 16804 which is Cat efficiency low. The MAF is relatively new. Any suggestions on how to proceed? Should I replace my O2 sensor? If so, which...