CO and HC emissions. I live in an area that requires emission testing. Kit cars fall under different, ie looser, standards, but standards none the less.
In GA the merto Atlanta area's emission testing is run by The Clean Air Force. I had communication with thier staff on the certification side and was assured it shouldn't be a problem. The requirements would be tailored to the configuration of the car.
I made my application and recieved notification that values had been established. Drove the car to a testing location and ran the car at idle and 2500 RPM, both in neutral. FAILED!
Along the way I have had conversations with various shops and mechanics about adjusting Weber carbs. I haven't found enough gray hair on mechanics to get the numbers met.
I have come to the conclusion that a Weber was designed to make power, damn the emissions!
I have driven on the street, but without a tag. I have only done this to get to workshops since it is illegal.
I can get a waiver for a year if enough $$$ is spent on repairs. I had the car at one shop that assured me they could handle the work. After 3 weeks if still hadn't passed. I was supplied with a padded bill, but they would not sign-off on the documentation needed to get a waiver. So converting to FI will consume enough $$$ (and some) to meet the amount for a waiver and with some work on a chassis dyne I hope to get some workable results.
Hope this answers you question.
Thanks,
Carl