www.epa.gov
Looks as though Calif. is gonna get tougher very soon..... Don't know much about the way they do things but I'm a Mo. IM240 repair tech here in St.Louis and you can't modify any thing on a vehicle 1971 up. we have to go thru a safety inspection that includes checking all the oem pullution controls that part is done at most any repair shop but then we gotta run to one of the states IM240 test stations for the sniff test on a dyno. $12 bucks for the safety & $24 for the emission only good thing is we now get 2 year license plates...