well i was reading this
http://www.rit.edu/~jxs1984/cars/200...R/100_0668.jpg

and it said "Variable Valve Dual Mode Muffler"

whats so special about that?

 

I think it goes something like this....

A flap is located in the muffler of the EVO so that at low RPM the flap is closed somewhat restricting the exhaust gasses flow. I think this is done to produce more low end torque. But during high RPM or when mashing on the gas this flap opens allowing less back pressure and better flow.

Maybe someone else can better explain.

 

that sounds about right to me, it's just one of those things that the dealer puts on there to make it sound like a really special deal, but it's not