Other than a cold air intake, what else can I do myself to boost my fuel economy? Thanks.

Inflate tires to maximum pressure. Vehicle will ride a little stiffer. Driving habits make a difference - slower, steady acceleration and coast to stops when practical.

Already do that.

Depending on what you are driving an aftermarket computer chip may or may not to available; and may or may not be effective.

I'd buy a Prius....... Lol

Have my daily already. This is just for my trapping truck

chip, tires, weight, lighter wheels. There's a lot more you can do

A truck?
Worst vehicle type out there.
remove unnecessary weight. Just you use this truck, no passengers, remove passenger seats. Got any brush bumpers, roll bars other dead weight, get rid of it.
Improve aerodynamics, get rid of large mirrors, find some small passenger sized mirrors, again with roll bars brush bumpers etc.
Tires, Get rid of heavy tires/rims, unnecessarily wide/large tires.

Drive like an old man, coast to stop signs and feather the gas away, stop being in a hurry. This is the biggest improvement you can make. I always get significantly better gas mileage than people with the same vehicle cause I drive in what my wife calls "old man mode".

Seriously, if your concerned about what you spend on gas you should never buy a pickup, look at smaller more efficient vehicles.
Don't let your ego drive vehicle buying decisions.

slow down. cruise at 60. speed up gentle and slow down the same way. keep your front end aligned. don't change lanes. same tire pressure in each tire. change plugs twice as often as recommended.

I put oversize tires on my pickup and it really hurt the fuel economy.
Back to the hydrogen argument.............I gained 2 mpg by building and installing a simple hydrogen producing unit. It was a pain to keep messing with so I quit using it. Buck isn't here to argue hydrogen anymore!

Trap out of your Prius.

I've stuffed a lot of rats, coon, beaver and deer in the back of my Focus while my pickup sits in the driveway.

Trucks suck gas....Just is.

Embrace the suck.

Anyone ever try the cow magnets on they’er fuel line ?

You can always go with a 4 banger 2WD.

Not sure what ur getting. My 2018 Silverado has the 5.3L and I’m getting 18.9 mpg. It’s not great but it’s better than the 13.5-14 I’d get with the 2004 Sierra and is a touch better than I’d get with my old S10. Having said that, they were paid for so...

The ideas listed above certainly help. No sense beating a dead horse.

Don't date fat chicks!

For safety reasons I would not put max air in the tires. JMO Get an old 4 cyc. take the driver seat out along with the back seat and cut into the trunk. Lots of space.

Suck is unavoidable. But it's a tiny tank, and I don't want to carry Jerry cans. Hence, why I asked a question that doesn't merit criticism.

A couple of people have mentioned getting a 4 cylinder. I had a 2013 Tacoma with a 4 cylinder. It got 20 miles per gallon. The oil change was at every 5,000 miles. Two years ago I bought a 2017 Tacoma. The 2017 is actually one size bigger than the 2013 was. This time I got a 6 cylinder for the extra power. Those 4 cylinders have to work too hard to move a truck, even a small one. The 2017 has the same exact oil, but now the oil changes are recommend at 10,000 miles, instead of 5000, because the engine does not have too work as hard. My gas mileage is at 21.7 miles per gallon. The 6 cylinder gets better mileage than the 4 cylinder did and it is even a slightly bigger truck. Those 4 cylinders might be just dandy for a compact car, but for even a small truck, they suck.

Before the deep snow I trap off a 4 wheel bike its a lot slower than the snowmachine but I can trap all day off the bike on a cup of gas.

I've tried lots of things but never had much success gaining very much.

Did have a guy tell me one time........
Put air shocks on the back to jack the rear up. You'll always be running down-hill and save so much gas, you'll have to stop once in awhile to drain some out.