[strych9]

Interesting take, but incorrect.

Engine mods in and of themselves don't add horsepower. However, they allow for better operating dynamics in which to create more horsepower, with tuning.

Look at the basics: an engine is essentially an air pump. There is a theoretical finite amount of air that can flow through an engine, limited only by its displacement.

Adding items like a cold air intake, headers, and cam are all working toward the same goal: allowing a greater amount of air to enter the cylinders at a higher velocity than the stock components will allow. The factory sets up the components for a good balance of durability, economy, emission control, and power.

Modders shouldn't care about economy or emission control, so when going for extra power, these items are not a major consideration. Putting those items at the back of the line frees up the ability to make more horsepower.

Back to the mod scenario. Now that we've added some items to increase air flow and velocity, properly tuning the engine computer adds the optimal amount of fuel and ignition timing control, and this combo adds more horsepower to the engine. Tuning is critical; if you add air, you MUST add fuel. Otherwise, the gains will be sub-par. Same as if we added more fuel without components: little, if any gains.

This is as simple as I could make it...