It’s illegal to install a used cat.
So you’re suggesting that the same people that would NOT install an aftermarket cat (because it’s illegal) WOULD install a used OEM cat, even though that is also illegal?
That makes absolutely no sense.
It’s pretty hard to prove that a used cat has been installed. Actually, it’s impossible.
They check for OEM converter during smog check in California and Colorado. You can’t register your car without a smog check. They have no way of knowing the converter was stolen unless it is was engraved with the previous car’s VIN.
So yes, that’s not only what I’m suggesting, it’s what’s actually happening.