I have been reading page after page and have yet to find the MPG tune, is there one out there... if so how does it work. What are the actual gains with a stock engine or moded with intake and exhaust.

Well i guess there is no MPG tune....so the factory setup is the best thing going for gas mileage ?

2.2 or 2.4? My 2.4 with a Trifecta tune running 87 gets close to 2 mpg better. when I run premium it gets close to 3 mpg better than the stock tune.

I believe in some instances, mods and a tuning will benefit you with increased mileage. That is primarily if you keep your foot out of the gas though.... easier said than done.
The benefits of increasing efficiency via parts and tuning can help by reducing the amount of fuel needed to achieve the same output.... theoretically.... I've done all sorts of stuff with my previous vehicles and not always noticed the claims made for such improvements, but I also usually beat the snot out of them since they performed better too.
I guess for the most part, it's always a craps shoot, but the potential is there.