Quote Originally Posted by f3racer View Post
Also what good does 4 inch tubing do when the opening to the throttle body is only 3 inches.
Well, not too too much of a difference for short sections. But to realize the difference, consider this exploitation:

The water tap outside of your house has the same outlet as a garden hose. Compare flow of turning the tap on without any garden hose attached. Now turn the tap on with as many garden hoses attached as you can. Pretty big difference.