how 2 kinda cheat a emission test

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my car failed HC AND CO BUT passed nox
all i did was advanced the timing a little and it passed everything with flying colours
(however i scoped my o2 sensor and it was a lazy bitch}
last 2 yrs ago it failed hc and co and it turned out 2 b the fuel regulator (leaks sending fuel into the intake under a bit of load}