Bad Pulley? Please help.

[Dude87]

I have a 98 mustang GT, My car is making a squeaking noise as I drive and the faster I go the louder it gets. I inspected my belt and the belt looks brand new. Some people have said its my pulley but how do I know which one it is? there so close together I cant tell, I think its but my tensioner but not sure. Do you guys have any good ideas on how to find out which one? How expensive are they and how are they hard to replace? Thanks for the help guys.

[Brent]

Take a decently long pipe and hold one end at the pulley an the other at your ear and move around to all the pulleys until you can isolate which one.