I have heard nasty things about 'spacers' and those 'tornado' things. Also, magnets for the fuel line, water injection and a slew of things.
Air intakes, by their own dyno charts, don't make any difference at all until 2,500 RPM and up and, as you said, you don't drive there.
I just took pichers of the exhaust of my 06 4.7 and son-of-a-gun if it doesn't already have 'mandrell bent' twists and turns as well as maybe a tuned exhaust manifold.
So, methinks there is not a lot that can be done to improve the in-and-out breathing without investing a bunch of money and that doesn't make sense.
I just installed Michelin LT 265/75R 16 tires. Someone, responding to my post on one of the sites told me to multiply the final MPG by 1.0308 to account for the larger diameter. Not enough miles to know for sure, but it seems I've picked up 1/2 mile.
I think the mileage is pretty much set by the computer and, without doing some adjusting of the parameters, our MPG will stay right at the 17 to 18 range.
I use and talk about, but don't sell Amsoil.
2006 Tundra replaced a
98 Dakota 3.9 automatic, long bed.
Retired with broken A/C, July 2008.
On original engine and transmission.
+Everybody knows something you don't know.
+Truth does not need to be 'balanced' and it ain't caused by voting or consensus or polls or yelling louder or silencing someone.
+Artists prove truth can be in forms you don't understand.