如果你的小老婆是california-spec的排气系统,catalyst converter会贵些。
Go back to the same shop and have them take a look. The part should have warranty (1 yr or 5 yr?). They could put in a new one if the original converter was defective. But you still have to pay for the labor of putting up the new converter.
$400 for catalyst converter job sounds too cheap. The retail price for catalyst converter is over $300+. The shop usually adds 10-20% markup on parts.
Good luck and let us know how it goes