Originally Posted by semtex

Hmm . . . if that were true, then how is it that people are able to commit suicide by piping exhaust gas into their cars. You know what I'm talking about right? Some people connect a hose to their tailpipe and channel the exhaust back into their car to kill themselves, and it's not like they remove their cats before doing this. Heck, some people just shut their garage doors with the car running and even that will do the trick. So obviously cats aren't reducing the CO levels to insignificant levels. With LTH, test pipes, etc., the difference is that the exhaust gases -- dangerous as they are -- are being ejected all the way out the back via the tailpipes. The gasses aren't leaking out underneath the car. If they were, that would indeed be cause for concern, and I don't think that changes just because you have stock cats on.

Now, having said all that, I don't think you need to worry unless you have a habit of just sitting in your car with the engine running at idle for extended periods of time. Just driving forward should negate any danger from the gap in your exhaust.