It's cool, I didn't take any offense, and I meant none as well. I'm hard to piss off either way :P
And correct. Remember that you could have a car with 300hp, drive it with the lightest foot possible, but you may get your butt handed to you by a little car that makes no power that runs /more/ efficiently in terms of your mileage. Making the car work/run/function better than what it is now.
Think of it this way. If a car that is already running really well gets 35mpg and you see things you can improve on (less weight, better aerodynamics and excellent driving habits) then you don't /need/ the extra power
you're letting the car better utilize the power and efficiency it already has and "unleashing" the potential in it in daily driving in doing more with what you have. Not sure if you've read the big list of things yet. But it's excellent. You can find that
Here 
and an even larger one
Here.
And yes, the CAI and Short ram is a power mod. You can /try/ it, but hook it up to something to see what mileage you are getting first, compare afterwards, you might get lucky. My guess is that your money will be spent better elsewhere though if you're looking for efficiency
If it helps as an example, the stock intake on my car is modified, but i bought nothing aftermarket, simply removed my resonators. Someone made a good point that it may not have doing that in which made it "more efficient", however, the purpose of me /not/ having bought an aftermarket intake for my car is that i've seen dyno charts, how it affected the car, and also the reported miles per gallon afterwards which was decreased. That's just for my car though, like i said, every ECU tunes differently, some even adapt to measurements differently though the concept is similar.
I've seen a few belly pan setups on here searching through the thread. Some people have used setups where they used aluminum sheets or other things like hard plastics and used bolts with clips on the end that "clip onto" the subframe or frame or part of the car so you aren't drilling into anything (if that's what you are worried about). In the thread in Daox's thread he uses choroplast (I'm assuming you can probably buy in sheets at home depot or what not).
I'm heavily considering doing a belly pan to my car and that would be the route i'd take because I don't want to drill into any part of my subframe or the car itself.
You want to use something though that will be rigid enough that it isn't going to flap in the wind or come loose.