I am an ex locksmith, and I know that you have to remove the ignition switch, key cylinder, and then remove the small metal tab inside the cylinder that the key touches when it is fully inserted. When the tab is removed...no more noise. To remove the lock cylinder, remove the plastic trim around the column, and then you should see the lock cylinder housing. With the key turned to the "ON" position you should be able to depress the pin the retains the cylinder in the housing and slide the unit out. Then remove the metal tab. ***These are only suggestions, and I claim no responsibility if any damage occurs.*** Attempt at your own risk!! But it really is pretty simple.
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1990 SHO, 5 Speed, New SHO Owner