Actually that's not quite true certain states don't have inspection requirements so they never check but any car that was built from the factory with the catalytic converter is required to have a catalytic converter to be a road. A catalytic converter contributes significantly to noise reduction. For most states that would be early '70s when the federal government mandated catalytic converters he same time they started phasing out leaded gasoline.
In California their emission requirements are much stricter and it doesn't matter if your car is classic or not all factory emission systems must be present. Now if you have a non-California version of a car that you bring into California it needs to comply to the emissions of wherever it was built but if you have a California version of a car that would have been stripped of its air pump and other things those need to be restored in order to get street legal in California.
Don't confuse the testing requirements with the requirements of the federal and state law.
> A catalytic converter contributes significantly to noise reduction.
It depends, but the muffler is what mostly reduces the noise. The difference between an OEM cat and a removed cat isn't always that much in my experience.
Yes, for cats it's 1975.
Interesting but unsurprising to know about California, but I have no reason to ever travel there via classic car, or really for any reason at all.
In California their emission requirements are much stricter and it doesn't matter if your car is classic or not all factory emission systems must be present. Now if you have a non-California version of a car that you bring into California it needs to comply to the emissions of wherever it was built but if you have a California version of a car that would have been stripped of its air pump and other things those need to be restored in order to get street legal in California.
Don't confuse the testing requirements with the requirements of the federal and state law.