One of the most well-known and easiest exterior engine modifications you can make is upgrading the air intake. It's an easy bolt-on procedure that takes less than an hour (typically) and can net you a few extra ponies by diminishing air flow restrictions caused by factory air intake equipment. Can anyone do it with a few simple hand tools? Yes, even your snot-nosed little brother can achieve this simple modification.
But don't expect that 50hp gain claimed on the side of some boxes. We'll tell you right now that we've dyno'ed countless air intake systems, and the absolute best increase in power we found was 20hp on a 5.3L Chevy V-8. But that is more than double what we find with most intakes-a freak of engineering, no less.
Airaid has taken the air induction game a little further by offering throttle body spacers along with their air intakes. Airaid's offshoot company, Poweraid, brands a line of throttle body spacers with a "helix bore" design that helps spin incoming air to provide a superior atomized fuel mixture (according to its website).
Off Road Evolution placed an Airaid intake and throttle body spacer onto a V-8 Nissan Titan in less than half an hour while we were working on another truck project.
 Mel Wade of Off Road Evolution...  Mel Wade of Off Road Evolution in Fullerton, California, first removed all the stock air intake equipment, leaving the lower part of the filter box since the Airaid system reuses that. |  Airaid's new upper housing...  Airaid's new upper housing clips and bolts directly to the lower factory airbox. |  Airaid provides a new MAP...  Airaid provides a new MAP sensor housing tube that goes in between the.... |
 .....new reusable Airaid conical...  .....new reusable Airaid conical filter and the factory air intake tube. |  The new Airaid washable and...  The new Airaid washable and reusable filter provides more filtering surface area to trap dirt in. |  Airaid not only sent us a...  Airaid not only sent us a Poweraid helix bore throttle body spacer for a little more low-end torque and power, but we also got this new Econoaid throttle body booster that advertises "Use less fuel, Get more power!" when used in conjunction with the Poweraid spacer. |
 The Poweraid throttle body...  The Poweraid throttle body spacer and Econoaid booster simply bolt together inline, and onto the intake manifold under the throttle body...... |  ......The Poweraid spacer...  ......The Poweraid spacer comes with a built-in O-ring since that's what seals the throttle body onto the intake manifold (instead of a gasket). | |