[jjflash]

Originally Posted by Danglerb

Factory cats are NOT high flow, they are old style air injection thermal reactors. Many are still good on 200k mile cars, but replace them with a modern design and you should pick up 5 or 10 hp and still be clean. The catch is that with some of the super high flow cats, running even a short time with a bad mixture can ruin them. I think there are reasonable choices that both flow pretty good, and last a long time. That said it may be hard to find a shop in Calif that is willing to install anything other than factory or Carb approved for that specific model.

So swapping the original factory cats back into a car with an X-pipe will work fine. I don't know how much trouble it would be to do it yet.

85/86 928 had a wider intake, requiring a special air filter box and intake tubes, which are NLA, no longer available. People frequently fail inspection trying to work around using the factory air filter box or intake tubes.

They fail the visual, or the sniffer/emissions? That would be something to keep in mind if an '85 or '86 came up. I guess the safe way to go would be to buy a California car and make sure the seller does the smog.

Thanks for the clarification!