California DMV engine change rules...?

looked up 66 smog specs..(in PPM and %?)
at idle: HC 700, CO 6.5
at 1500 HC 500, CO 4.0
(No NOx was measured or cared about as they hadn't linked SMOG with NOx yet)

82 specs are idle (?) HC 63.2, CO .37 NOx 850
xx xxxxx *** 15mph HC 139, CO .43 NOx 1315
xx xxxxx *** 25mph HC 205, CO 2.16 NOx 2260

Look at the reduction of HC (hydrocarbons) over the years, no wonder LA skies are not (always) brown anymore.