A while back ago a friend of mine gave me his intake tube from his nissan he was driving. I didnt think anything of it and threw it in the back of my shed. Yesterday when I was looking for some soap I found it and started to wonder if this would fit my car. I measured the diamater and sure enough it is 3". Then I took off the intake I have now and see if the angle was going to be good, and with some cutting it can fit, however the tube is a little small for my TB. I measured the tube again and again it was 3", but when I measured my TB it came out closer to 3 1/2". If everyone is using a 3" diamater tube, then how is it securely clamped to the TB? Does the intake actually go a little bit in to the TB and it is held there with some type of rubber clamp?

You'll want a reducer or coupler. Siliocone is the best, but any pipe clamp fromt a store will work. They're normally bigger then 3" before clamping.

So if I get the reducer and use the intake tube, it wont do anything negative to my car since the two objects are 1/2" different then each other? Because I have heard that using a 4" tube will be less productive.

3" on N/A. Your throttle body is 3" in the back, where it hooks up to the intake manifold.

So with the tube, I can take off the maf screen and slide it in until the tube hits the back of the TB? Or should it only be halfway in or not at all?

Don't put it in the TB. Keeping them connected by the coupler is best. You could get some false knock, sraping, damage to TB, etc. If you hit the back of the TB you'd go thru the plate...

Allright. Any ideas off the top of your head where I can get a coupler? Does Home Depot or True Value sell them, and you said get the silicone kind. Is rubber or something else ok, as long as it does not melt, right?

Rubber is too rigid, and doesn't allow the intake pipe to flex independently from the motor torque (rocking in the mounts). Rubber also transfers heat better than silicone, which is undesirable. Rubber also hardens and cracks when it goes through many cold/heat cycles.

Getting a reducer from a turbo supply story or something similar is preferable, if it'* in your budget.

Allright, so most likely like Jegs or JC Whitney? The coupler should be 3.5" to a 3", right? A turbo reducer, is that what you got willwren?

Sounds right to me. I have no idea where mine came from. It came with my intake. I know it'* silicone, and I know it was made in Austrailia