Ya know, I've been playing with these little two cycle screamers for years when none of them had mufflers. Some didn't even have an exhaust port, just three or four slots at the bottom of the cylinder. So, what damage would it do to run them without the muffler? The only reason we started to use mufflers in the first place was to hold the noise down and not be harassed by the cops called by the local residents. I suppose that today it's a matter of national security, ya think?