[pgfpro]

First things first, thanks for the insightful comment's and discussion.

Let me come at this another way. Take your basic premise improving fuel economy of your daily driver. You've covered all basics already tune-up, tire pressure so on so forth. I myself would start like this:

1.) reduce wheel dia. and mount lower profile tires within reason to lower the relative effective gear ratio of the rear-end or trans-axle. this may also improve aerodynamics too, by lowering ride height.
My car is 2" lower then stock. Its a pain getting in and out of but helps with the aero.
2.) better air filter
I'm running a after market air cleaner.

3.) on the exhaust side; header(s), free flowing catalytic converter, muffler
I'm running a aftermarket free flowing exhaust system with a e cut out.

4.) replace camshaft with one that develops torque at earlier rpm range ( they used to call RV grinds )
I'm running a performance vtec cam. It has a low profile and high profile.
5.) have automatic trans modified or replace with manual unit
manual trans

6.) lower rear-end or trans-axle gear ratio ( example: 3.73:1 to 3.42:1 or 2.73:1 ), keep in mind a lower gear ratio requires more torque, but that's where the smaller dia. wheel and tire package really helps out
This is where I could see some improvements at freeway speed is to bring my rpm down some.
7.) install a second battery, battery selector switch, alternator cutout switch, and a solar cell battery charger, ( most of these item's preferable marine grade, deep cycle hold a charge longer, selector switch should be able either battery, both or off, also acts theft deterrent, alternator cutout should be rated twice the ampere output, and suitable fused )I need to look into this also.
8.) now lets add a gauge package: vacuum, amp, second voltmeter, fuel pressure, and transmission temp. ( vacuum can be labeled fuel economy, amp lets you know the batteries state of charge or discharge, should be selectable to either battery or wire in a second one, and transmission temp. helps with peace of mind whether auto or manual, after pricey mods )I'm running a boost vac gauge and my efi software lets me monitor all these things. So that's a plus.
9.) lets improve lubrication: aftermarket oil coolers for engine and trans, even additional engine, plus trans fluid filter. I still need to take advantage of this.

10.) if equipped to handle E85, change fuel system components: aftermarket fuel cell, fuel pump, fuel pressure regulator, fuel line (combination stainless steel and flexible braided), aftermarket fuel delivery components rated to handle E85

note; there have been a couple of published studies done on the effects lower grades ethanol blends on non E85 equipped vehicles I'm running after market fuel rail and fuel lines to help with the e85 when I race the car.11.) suitable used laptop with software to benchmark, monitor, and troubleshoot:I'm running Neptune efi software

12.) enhanced driving techniques for r & d to pull it altogether Working on driving skills.
Future mods would most likely include engine rebuild, balance and blueprint, rework, port match and bench-flow heads My engine is built with a ton of mods.
That should be enough for most average modders to handle.

P. S. Oh, I almost forgot the intake system, stay tuned got to get some sleep for 2nd shift. Keep on wrenchin, let know what you think.

Thanks for the input. I think my biggest gains now will be all aero.