OK,
I'll take the bait.
You can add Power and Increase MPG. The two can certainly go together assuming you were not using the fuel most efficiently before the mod was made.
I see it all the time in our large bore medium speed engines putting out some 1,300 hp per cyclinder, with a total of 18 cylinders. These are single engines putting out some 24,000 hp each.
There are plenty of ways of doing this. Boosting charge air pressure by improving efficiency of the turbos (tweaking with the pitch of the nozzles and/or turbine blades, use of anti-fouling materials, etc...). Basically you are making the turbo more efficient at using the waste gas and heat. You can get more power and you can improve efficiency.
Another way is to tweak with inlet and exhaust valve overlap. This used to require replacing valve cams but now they have electronic adjustable cams that can shift forward or reverse to advance or retard valve opening.
Same goes for fuel injection. You can improve the design of the injector tip, improving atomization and spray pattern.
You can also tweak with the piston crown, changing the shape and contours, increasing compression ratio and improving the swirl effect during injection and combustion.
In some large diesel engines recently they are using something called Miller Cycle which requires higher charge air pressure (so very efficent turbos) with increased valve overlap timing (which makes the increased charge air pressure actually push the piston downward near the bottom of the combustion stroke. These engines have demonstrated markedly better fuel efficiency with same or better power.
Now the hot item is same as seen with our diesel cars, electronic common rail fuel injection, where you have highly accurate timing of start and end of fuel injection.
You can also employ high tech ceramic materials and coatings that retain heat better and use TBC (Thermal Barrier Coatings).
So, in conclusion, there are plenty of modifications that can increase power and increase MPG.:thumbup: