ISC spacer?

I just bought a spacer for my idle speed controller. I was told by a local mustang shop that it was designed to help with the idle. They said it was Ford's "cheap fix" for idle problems. They said they had never seen a '93 engine without one. They weren't trying to rip me off, they sent me to Ford to buy one.

Does anybody have any more information on this spacer? I'm about to put it on, but I don't know how to set the ISC. Don't you have to screw in two screws or something?

Thanks!

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