I was wondering if any of you guys or gals know exactly how a muffler on or off of a quad affects the performance. I know that some types of engines need a certain amount of backpressure to assist the valves. Is this also the case on a quad? Also, does anybody make an aftermarket muffler that is SUPER QUIET? I would like to tune down the noise a little fer sneaking around in the woods. Anybody have any ideas as to how to modify a factory muffler to help silence it? How would something like this affect the engine?