Does anyone know what the effects of different sizes of intake tubes do to our engines? I know that if you go too small you lose power, but what happens if you go too large? If anyone knows of any formulas for this, that would be great.
I am just curious as to what the effects are on our engine, and how to find the "perfect" diameter, if there even is such a thing.

You cant go to big because you car will only take as much air as it can handle. On the other hand you can go to small.

It would depend if you were channeling air into your system or not. If its just setting in your engine compartment then it doesnt matter but a 3 inch works well and fits directly to the TB. If you are going to being doing some ram air the 3 inch will get you more hp at lower speeds and something such as a 4in will help at highway speeds more.