check engine light and airbag light failure

hell everyone i am new ti the forum and i just want it to ask to the people with more experience than me; my check engine light went off a while ago, i went to the dealer and they diagnose my car saying that i need a new catalic converter wich it cost original almost a ridiculous amount of $2,000. i went to another place and they said that is probablymy air sensor that usually when they diagnose thet car and is a cat problem it mught be the air sensor. also my air bag failure light came on. please , is there is somebody who know about this situation post me a solution and if i have to get and new catalic converter , suggest me with the best one aftermarket. And i want it to ask wich supercharger will work better with my car, i'm thinfing on getting one

if your car has 7rs or 70k miles or less on it than its federal emissions warranty and it should have been free. if you had more, sorry to hear that.