I have a 93 civic si with 227000 miles I repalced the cat a year ago and I failed smog, just barely, in northern california.
Hydrocarbons (HC)
15MPH. . . . 93. 21 . 93
25mph. . . . 59 . 13 . 60
Everything else was fine.
I read some of the suggestions below and I was wondering if they would work in my case as well?