Just wondering if anyone knows if you need a muffler and a cat converter or just a cat converter to pass emissions in MO. Thanks

 

They do hook up to your OBD-II port to run it for emissions codes, but they do not use a sniffer.

In for an answer, i know your supposed to have a cat, but im not sure about a muffler.

 

Not all vehicles come with mufflers. And I believe the law doesnt state you need one. I think it just states your exhaust needs to be in good working order. However if you fail I believe you have 30 days to go back after repairs and not need to pay for the inspections again.

Though you will need a cat as the place is supposed to do a visual inspection and you can fail for not having one.

As far as the OBDII part as long as your check engine light isnt on and you havent cleared the codes or unplugged the battery in the last 30-100 miles (ecu does readiness tests and it wont show ready) then you should be fine.