There is a "popping" noise when I slightly turn the wheel left of right fairly slowly, as in just making the normal small corrections while driving on the road, the popping sound will occur. It may be the squeaking sound already mention but this sounds more like popping.
Steering Issue on 1998 Ford Mustang
Usually the first thing to check is the stabilizer bar (sway bar) and the rebuild kit is fairly inexpensive $20 to $40 plus about an hours labor. But it could be any part of the front suspension that has worn out and should be inspected by a repair shop and you can locate one here www.repairpal.com/directory