Performance Mods = FE Increase?!?

[Mightymouse13]

Okay ladies and gents, I'm looking for some feedback on a touchy issue. Performance modifications that lead to fuel efficiency increases. I'm wrestling with my theory on this and could use your input.

Lets examine a "high performance" exhaust system. Tuned equal length header, larger than stock mid-pipe, and performance axle-back muffler. Now generally speaking, 9-times-out-of-10, exhaust systems like this only increase torque and horsepower at max rpm's. Also, 9-times-out-of-10 there is usually a loss of hp and torque at the lower rpms, specifically at normal highway rpm's.

Now, lets say your Yaris, Fit, Prius, or whatever operates at 2500rpm at your highway cruising speed. Lets also say that your new "performance" exhaust lost 7lbs. ft of torque at that rpm. Since you have reduced available power you now have to increase throttle to compensate, thus reducing your gas mileage...correct?

I've been searching and searching for exhaust products that actually demonstrate a dyno-proven GAIN in torque at low rpms and I have found a few. I am hoping you FE scientists will confirm my theory.

If I increase torque at my 2500rpm highway cruising speed by lets say 10lbs-ft I now have MORE available power and should be able to use less throttle and therefor less fuel. Does this sound correct?

Your thoughts? I would essentially be increasing engine efficiency by reducing parasitic power loss.

Also...this is a "if money was no object" discussion. Yes, spending $1000 to gain 1mpg does not make much sense....I'm more concerned about the theory behind it.