I have several questions about mufflers only, not the entire exhaust system. Is their main purpose for noise suppression? Other than disturbing the peace, are there any negative effects to the engine without one? Are they necessary for proper engine operation and for maximum fuel effeciency?

 

I saw a youtube video of someone's OBS with just a straight pipe, and it sounded damned cool. Just curious about these questions and welcome your opinions. Thanks.

A straight pipe usually means running without cats, or gutted cats, not just no muffler.

 

Some engines require a certain amount of backpressure in the exhaust for the exhaust valves to close properly.

Keep in mind your local sound ordinance as well, don't want to get a ticket having it too loud. Go on ebay you can find good exhaust kits all day long.