So lets imagine that you and your significant other just finished a bottle of wine… Now take a look at the bottle and lets imagine that the more part under the skinny neck (you not the bigger part) is the motor of an engine. Now you see all that air stored in the bottom part of the bottle, thats engine exhaust. Well what are you waiting for, take all that air that the engine has and push out the thin little neck. That is what the engine is trying to do every time one revolution of the engine goes through and then your engine is idling at 2,000 rpm. Yes that is revolutions per minute.
I was trying to get a point across and I dont know if I did. For every one revolution your engine goes through, it takes air and fuel, ignites it and the left over, carbon dioxide, is expelled. So as a professional in the field of performance accessories, I can say: A stock exhaust is not made for optimal performance. Well you cant really blame the automobile producers. They have to worry about noise and pollution (which are mandatory by laws); cost of producing millions of each individual component, the list is endless.
So the answer is a better performing exhaust by a...