It will take some digging to get at, but you need to check the intake runner changeover butterfly shaft in the lower part of the intake. The shaft bushings wear too easy, and leak a lot of air, making for a very high idle. Also check for vacuum leaks elsewhere in the vac lines (I use a piece of vac hose to the ear and trace the other end over the lines, listening for a whistling sound of the leak leakin'.

The black ISC is a superior part to the old beige one. Reinstall it, after you test out the coils per the fsm.

90% sure it's an intake leak of some kind...