Looks like the cruise control cable.
You don't have a throttle cable on an SC, it is a solid linkage. The cruise control is cable actuated, with the cable running from above the throttle body to a black cannister looking thing outboard of the left shock tower.
Is this it?
Your servo probably looks a little different, as the cable isn't attached in this photo.
If you don't use your cruise control, you can just remove the cable. If you do, use it, Pelican carries the replacement.
http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_Pcable_pg4.htm#item9
Are you sure it was the cable causing the problem, and not the cruise control? Holding the engine at a specific RPM is kind of its job.
Tom