vacuum?
 

Hey guys,
This is my first post and I am definitely sure it won't be my last. I just bought a mustang with a 4.6 in it from an auction and I am going to need your help. First of all, when the car is started and running I can hear a loud whistling (sucking) coming from what sounds like the throttle body. I am thinking it is some kind of vacuum leak. When the car is in idle it is pretty smooth, but when in gear(automatic) it stutters and shakes. Also, my cruise control and my (air, a/c, vent, heater) only blows out of the defrost vent. This is kind of convincing me that it is a vacuum leak. Any help would be awesome and if you've got questions ask away.

Look behind the TB towards the firewall, right in the middle there is a vacuum line going into the intake plate. Check to see if it is cracked, this happened to me when I replaced my manifold. The old hose had a hairline crack in it, and when I went to put it back on, it split-- I figured out what happened real quick when I cranked the engine. Also, check the gasket between the EGR on the driver side and where it connects to the upper intake piece. Otherwise there are a couple other small hoses in that general area