With engines getting as complicated as they are nowadays, it's no wonder that improving airflow into your engine is one of the first mods a typical owner makes. Improving efficiency on the outsideof the engine with a bunch of bolt-ons is much cheaper (and much more legal) than getting inside a computer-controlled fuel-injected motor. And even if you did modify your fuelie, you're going to need to increase airflow into that engine to make that extra power.
We're sure you've heard how good or bad or worthless or wonderful an air intake can be on a newer vehicle, but it is one of the first mods you have to make to really utilize any power you want to make with other mods like exhaust, or dumping more fuel into the engine via tuning.
What works and what doesn't varies from engine to engine. Your best bet is to ask a couple of common truck owners what they've had success with before you spend your entire paycheck on every throttle body, air swirler, throttle-body spacer, and frozen air intake you can find for your application.
For high-end air-filtering elements, you have two common choices: a cotton gauze/oil mixture, or a DryFlow material that uses no oil and filters the air dry, like a paper element. The DryFlow media does not have oil to mess with, so you cannot under-oil or over-oil it. The cotton gauze and oil-filtering media is difficult to clean and oil, but filters the air well when properly oiled.
There is a lot of controversy over the legitimacy of throttle-body spacers. We can tell you that they definitely work (to improve power and fuel mileage) on some engines, while others we couldn't tell.
This is Poweraid's helix-bore throttle-body spacer for a Jeep 4.0L, and throttle-body spacers definitely work on 4.0L engines. The way the throttle body mounts on the intake manifold, air is shoved directly into the wall of the intake manifold. Because the air has such a short distance to go, it still has a lot of velocity when it bounces back off the intake manifold and directly at more incoming air, thus blocking incoming air. Adding a throttle-body spacer adds more runway for that air to go through, and the helix bore on this Poweraid helps swirl the air down so it enters the intake manifold and spreads sideways into the runners of the intake manifold.
Replacing the throttle body on your fuel-injected engine can also be a good way to improve airflow into the engine. Aftermarket throttle bodies like this Holley unit for an '87-'95 TBI Chevy 350 can have larger throttle bores, shaved throttle shafts, and smoothed plate screws to further reduce friction as air flows into the engine. Another nice feature of this two-barrel Holley is the two-connector setup converted into a single connector connection.
Adding a complete air-induction system like one of the new Fram Boost units can really make a difference over just adding a new filter. The smooth air tubes allow for much less turbulent flow than a factory air-induction system that has outlets and offshoots for silencers. One thing we really like about the Fram Boost air-intake kits is that we can pick them up in any auto parts store that carries Fram replacement filters.
We chose to remove the factory air-intake box out of this 5.3L Tahoe due to its restricting design. AEM had a Brute Force cold-air intake kit for this truck that fit perfectly in place of that factory plastic.
This AEM kit utilizes all the factory sensors, and has accommodations to fit them into its design. It also keeps true to being a cold-air intake box, keeping out much of the engine compartment's heat. This 5.3L Tahoe kit is an extreme example of how well a cold-air intake system can work (and is one of AEM's best performing kits) as not all kits will give even half this much horsepower, but this particular Tahoe made 20 horsies.