Can better Exhaust system give better MPG?

Here this guy claims 15-20% more power can be had with a better exhaust system, "instead of being wasted by the exhaust system".

While the main reason for such mods appears to be HP (horsepower) gains, shouldn't that also translate in some way at least to better MPG?

Just as removing A/C takes a load off the motor, and increases MPG, shouldn't the load from the exhaust system also free up power with an increase in MPG?

http://www.youtube.com/watch?v=vgCOlOWiFiQ

I believe in the old saying more air IN, most exhaust OUT, the MORE GAS is burned. Heck our 93 Lumina only has a cat & muffler. When the muffler burns out I might put a straight throught muffler on it. The OEM only has lasted 240,000 miles & 15 years. So I might not live long enough to change out the muffler.

I believe in the old saying more air IN, most exhaust OUT, the MORE GAS is burned. Heck our 93 Lumina only has a cat & muffler. When the muffler burns out I might put a straight throught muffler on it. The OEM only has lasted 240,000 miles & 15 years. So I might not live long enough to change out the muffler.

Well, up here in Canada where they put enough salt on the roads to turn Iron Man into a pile of rust, my mufflers (probably not OEM) are cracking open and making extra noise already, at a mere 180,000 kilometers. Of course somebody may have wound the odometer back a few times before I got it (it seems to be a popular practice among used car dealers).

So the point is, with brackets rotting off and mufflers going south, I might as well think through the next "Mr Muffler" visit while I'm there.

If I were to put on some noisey "thrush mufflers" along with an oversize tailpipe, and put a bigger air scoop on the intake too, can't I make horsepower gains, and also MPG gains while I'm here if I drive carefully?

For instance, suppose I'm chugging up a hill in first: Now with my weak engine, it must take longer and burn more fuel less efficiently in terms of translating whatever power is in the gas to the road. If I've got an easier load on the engine for the same hill, and same cargo, ain't I gonna burn less gas up the hill, and do so more efficiently, providing I don't do anything stupid like try to accelerate or gun the engine?

One of the supposedly biggest tips for gas savings is "don't accelerate uphill." Wouldn't that indicate that MPG in some situations at least could benefit from more HP?