In most places which have emissions testing, not only is there a smog test (where they attach your car to a computer), there's also a visual test. The inspector views to see that all emissions equipment is in place. Without your cats in place, this is an automatic fail.
Also without your cats in place, assuming since you said catS this is an OBDII vehicle, your check engine light (CEL) will illuminate due to the downstream O2 sensors either being eliminated or not reading correctly due to the lack of cat function. This, too, is an automatic fail at most testing places.
There are ways around these issues. You can purchase a set of aftermarket high flow cats which you can place after the collectors. Contrary to popular belief, cats don't restrict your exhaust flow unless clogged. This would require some exhaust work, but you're going to have to do this anyway. If Canada is anything like California in how they deal with emissions, this may be harder than it seems, though. You will want to check with the local laws to ensure you are doing the right thing before you waste a lot of money and time just to figure out it's still against the law.
Even with cats at the end of your headers, they won't be as efficient as they are on your stock system, mainly because they sit farther down the exhaust stream, which gives the exhaust time to cool. This makes the cats not heat up as well which is a key ingredient in how they work.
An alternative is to get shorty headers which will mate up to your stock exhaust. They basically replace the manifolds which come stock with tubular headers. While these won't provide as much of a performance boost, they do provide some and will still allow you to maintain your stock exhaust from the headers back. It's a fairly good trade off in the long run.