It's the VCV, top center of your diagram, that controls the EGR.
**** wait! I may be wrong****
I'm not all familiar with these older F-100's, and I see your truck has that crazy valve in the exhaust.
It may control that, and the thing isn't functional anymore, so the OP decided to disconnect it.
Sorry I jumped the gun.
I'm used to mid '80's 5.0's, but not the earlier trucks.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.