okay, let get things spicy a little in here..

I have a doubt, according to what Gouki's posted (http://www.sportcompactcarweb.com/tech/991...xhaust_systems/) I got confused on what is backpressure. At first, it stated there that the exhaust at least needs backpressure and while you keep on reading, it will says that engine doesnt need backpressure. Now, what is the difference between this two? The exhaust needs backpressure? But why?

Aside from changing the muffler unit, why not redo the tubing of the exhaust to gain power? Does this can be done? Use new tubing size from CC to muffler and ends with original muffler. How?

I think I happened to read in NST Car,Bikes and Trucks regarding backpressure.

Assuming that after the exhaust cycle, exhaust exiting the pipe flows in high velocity, creating a vacuum as it leaves the pipe.

But, before the gas fully left, the vacuum effect siphoned the air-gas mixture before the valve fully closed in such rapid movement. Without the necessary pressure to helps the valve close in time, air-gas mixture exits with the exhaust together, resulting in the waste of unburnt air-gas mixture (gas is gasoline, or fuel).

Well, that's what it says and why those big MILO TIN is having ultra high FC, loud rumbling of an asthmatic elephant but no power to fart.