KKM/K&M, TB size, exhaust set-up, chip..?

[Goober]

After reading tons of material on this subject, I'm still a tad confused as to which of these set-ups are the best, as far as mileage, hp, etc..Does the KKM work better with a throttle-body of one size, while the K&M works better with the stock set-up,..etc...I hope you can see where this is going. A 2.5" exhaust vs. the 3", with which muffler for sound/performance,..etc..which chip works better for which set-up. I know there are probably endless set-ups for this, but I'm just trying to get the best way.
Basically, I'm looking for retaining the better mileage quality while getting a few more ponies and getting reliability. Thanks.