Depends on whether or not they do a visual inspection. I'd almost guarantee you'd fail a visual inspection if they knew what they were looking for - as the factory primary catalyst is visible from under the hood. Really depends on the state and what the regulations and methods of inspection are. I'd check with your individual state or with MS3 owners in your state who have been through the inspection and can give you advice on what they have seen in the situation. There's really no way for us to keep up on emissions laws and inspection methods in 50 different states and other countries. We sell our parts internationally and there are a number of items we run into in relation to emissions with those customers pretty regularly.
For example, in Australia, the factory airbox is inspected to be intact and open element air filters are frowned upon, so we sell lots of turbo inlet pipes to Australians but not as many intakes. We had a customer in Germany who needed a 400 cell catalyst in order to pass inspection recently as well. There are just so many options here in the US and around the world, it becomes prohibitive for us to keep track of them and to track any changes in regulations.
Jason
CorkSport