347 Big Time Idle problem

[89FHPLX]

Hey guys, this is for a friend of mine. recently he's been haveing a problem with is Idle. he bought a new Idle control or whatever you call it. You know the thing that's next to the TB with a plug that connects to it. Well the deal is that his RPM goes to 2000 2500 on Idle. When he unplugs the unit, the Idle stays where it should be or lower. I gave him me old TB from my 89 Stang. He took of the Idle control (whatever the name is) and it did the same thing. can it be a vaccume leak? or something else. This might some familiar to some of you that might had this problem in the past.


Thanks for the help