An old 740? All it has to do is pass the sniffer check at inspection time, they don’t care how the car passes, only that it does. The standard applied is one in force when the vehicle was manufactured.
Now, it may not be possible to get it through officially running catless. What many drivers don’t know is that the more unburnt hydrocarbon there is in the exhaust gas, the better the cat actually works. So, many manufacturers set their cars up to run rich in open loop mode to improve cat efficiency and obtain a cleaner exhaust. It wastes fuel, but it’s easier and cheaper (for them) than the alternatives. Anyway, the result is that the car runs pig rich, so if you remove the cat from the system all that unburnt hydrocarbon filth comes pouring out the tailpipe instead of getting turned into something less toxic in the cat. You will not pass a real sniffer test like this. Performance tuned cars can pass pretty stringent emissions tests with no cats at all, but note the proviso ‘performance tuned’. It takes an expert hours of time on the dyno to pull this off and the settings that are arrived at are good on that car only. There’s no way this could be done on mass-produced vehicles.
So, there are three possibilities for you:
- Just get a replacement cat. The junkyards are full of good ones.
- Get the car properly tuned to run lean and clean and catless. May be difficult on your car, and more expensive than buying a new cat.
- Slip the inspection shop a few grand to fake the sniffer test every year and go catless anyway. In the long term, no cheaper than buying a new cat.
Disclaimer: I do not condone running a street vehicle catless unless properly tuned to a state where it would pass the emissions test applicable for it’s year of manufacture. I do not condone cheating on emissions tests or bribing others to do so.