I am having a problem that hopefully somebody here can help me with. The car has a bone stock speed density motor. The problem is that no matter what I do, I cannot get the idle to come down lower than 1500. The throttle body is closed all the way and is still revving. There are no vaccum leaks(as far as gaskets), but it is obviously sucking air from somewhere. If I pull the PCV valve out while the engine is running and plug the end of it with my finger, the car idles beautifuly(after idle screw is put back to proper position). Also, when the engine is running, if you take the tube off of the valve cover (the one that goes to throttle body), air is being sucked into the engine through this hole.....wait.....there's more.....There is a vaccum line that goes from the vaccum tree on the underside of the intake that ends at the MAP sensor. If I pinch this line off, the engine will spit and sputter or even stall out. I know that on my last two mustangs (which both had mass air)there wasnt even a line going to the MAP sensor. The car runs very good besides the idle, doesn't smoke, only has 48K miles on it. It does lean out if you get on it, probably because its getting more air than the computer realizes, I would imagine.......................please help!!!!