Just put an intake on but having trouble

first off let me start by saying that the person before me had the normal black airbox in it but no filter. I later bought an intake and put it on but now when I am slowing down and even when I stop, It revs up and down by its self what should I do???:mad:

you have a vacuum leak. check all the lines you disconnected to install the intake and make sure you have the right vacuum lines connected. doublecheck the back of the plenum, right behind the throttlebody... i had to remove a line from there to install my intake, but you have to cap it off or it becomes a vacuum leak that sends your computer on the fritz in idle.

Like Drift said, check all your lines.:)

why didn't the person before you have a filter?

I have no idea! Maybe they thought of it being a cold air intake?!? My $hit was dirty as a mutha though.